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	$144.97	5.635%	$153.1391	$153.14	$153.15	$153.10
Purchase #2	$120.73	6.504%	$128.5823	$128.58	$128.60	$128.60
Purchase #3	$244.62	8.105%	$264.4465	$264.45	$264.45	$264.40
Purchase #4	$196.68	12.538%	$221.3397	$221.34	$221.35	$221.30
Purchase #5	$247.69	6.207%	$263.0641	$263.06	$263.05	$263.10
Purchase #6	$139.83	11.170%	$155.449	$155.45	$155.45	$155.40
Purchase #7	$70.76	10.353%	$78.0858	$78.09	$78.10	$78.10
7 purchase totals =	$1,165.28		$1,264.1065	$1,264.11	$1,264.15	$1,264.00