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	$151.74	8.775%	$165.0552	$165.06	$165.05	$165.10
Purchase #2	$174.27	9.263%	$190.4126	$190.41	$190.40	$190.40
Purchase #3	$141.69	12.585%	$159.5217	$159.52	$159.50	$159.50
Purchase #4	$49.34	9.691%	$54.1215	$54.12	$54.10	$54.10
Purchase #5	$146.68	3.426%	$151.7053	$151.71	$151.70	$151.70
Purchase #6	$203.54	4.265%	$212.221	$212.22	$212.20	$212.20
Purchase #7	$149.68	12.549%	$168.4633	$168.46	$168.45	$168.50
7 purchase totals =	$1,016.94		$1,101.5006	$1,101.50	$1,101.40	$1,101.50