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	$162.35	9.706%	$178.1077	$178.11	$178.10	$178.10
Purchase #2	$71.37	3.227%	$73.6731	$73.67	$73.65	$73.70
Purchase #3	$20.41	4.429%	$21.314	$21.31	$21.30	$21.30
Purchase #4	$103.86	4.119%	$108.138	$108.14	$108.15	$108.10
Purchase #5	$54.80	11.408%	$61.0516	$61.05	$61.05	$61.10
Purchase #6	$60.33	3.672%	$62.5453	$62.55	$62.55	$62.50
Purchase #7	$65.82	10.713%	$72.8713	$72.87	$72.85	$72.90
7 purchase totals =	$538.94		$577.7010	$577.70	$577.65	$577.70