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	$64.58	9.179%	$70.5078	$70.51	$70.50	$70.50
Purchase #2	$36.28	3.612%	$37.5904	$37.59	$37.60	$37.60
Purchase #3	$63.25	12.148%	$70.9336	$70.93	$70.95	$70.90
Purchase #4	$200.52	7.233%	$215.0236	$215.02	$215.00	$215.00
Purchase #5	$226.35	3.506%	$234.2858	$234.29	$234.30	$234.30
Purchase #6	$54.94	12.300%	$61.6976	$61.70	$61.70	$61.70
Purchase #7	$44.78	8.385%	$48.5348	$48.53	$48.55	$48.50
7 purchase totals =	$690.70		$738.5736	$738.57	$738.60	$738.50