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	$53.37	5.227%	$56.1596	$56.16	$56.15	$56.20
Purchase #2	$180.58	4.431%	$188.5815	$188.58	$188.60	$188.60
Purchase #3	$249.90	11.234%	$277.9738	$277.97	$277.95	$278.00
Purchase #4	$70.51	8.527%	$76.5224	$76.52	$76.50	$76.50
Purchase #5	$73.34	7.573%	$78.894	$78.89	$78.90	$78.90
Purchase #6	$108.46	9.782%	$119.0696	$119.07	$119.05	$119.10
Purchase #7	$247.31	10.267%	$272.7013	$272.70	$272.70	$272.70
7 purchase totals =	$983.47		$1,069.9022	$1,069.89	$1,069.85	$1,070.00