Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$209.95	10.301%	$231.5769	$231.58	$231.60	$231.60
Purchase #2	$199.64	11.126%	$221.8519	$221.85	$221.85	$221.90
Purchase #3	$5.59	9.256%	$6.1074	$6.11	$6.10	$6.10
Purchase #4	$239.39	8.162%	$258.929	$258.93	$258.95	$258.90
Purchase #5	$143.54	6.207%	$152.4495	$152.45	$152.45	$152.40
Purchase #6	$77.85	9.844%	$85.5136	$85.51	$85.50	$85.50
Purchase #7	$113.51	9.871%	$124.7146	$124.71	$124.70	$124.70
7 purchase totals =	$989.47		$1,081.1429	$1,081.14	$1,081.15	$1,081.10