I always round to either leave a 0 or to raise to .50. DC counts each charge as the basis of their rounding so a charge of $10.49 gets 10 and a charge of $10.50 gets 11 - that's the points for the charge. They now participate in iDine so you get 20% or 40% off on certain restaurants. Haven't tried my DC on restaurants that give less but it is listed as 15% not 14% off.
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Ms.DtG