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	$147.53	5.456%	$155.5792	$155.58	$155.60	$155.60
Purchase #2	$248.25	3.142%	$256.05	$256.05	$256.05	$256.10
Purchase #3	$179.83	9.123%	$196.2359	$196.24	$196.25	$196.20
Purchase #4	$42.76	8.669%	$46.4669	$46.47	$46.45	$46.50
Purchase #5	$6.37	12.649%	$7.1757	$7.18	$7.20	$7.20
Purchase #6	$199.46	4.668%	$208.7708	$208.77	$208.75	$208.80
Purchase #7	$55.97	9.680%	$61.3879	$61.39	$61.40	$61.40
7 purchase totals =	$880.17		$931.6664	$931.68	$931.70	$931.80