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	$178.40	3.434%	$184.5263	$184.53	$184.55	$184.50
Purchase #2	$90.75	5.359%	$95.6133	$95.61	$95.60	$95.60
Purchase #3	$235.98	5.681%	$249.386	$249.39	$249.40	$249.40
Purchase #4	$67.95	6.634%	$72.4578	$72.46	$72.45	$72.50
Purchase #5	$69.55	13.819%	$79.1611	$79.16	$79.15	$79.20
Purchase #6	$61.29	9.784%	$67.2866	$67.29	$67.30	$67.30
Purchase #7	$51.37	3.613%	$53.226	$53.23	$53.25	$53.20
7 purchase totals =	$755.29		$801.6571	$801.67	$801.70	$801.70