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	$133.90	13.504%	$151.9819	$151.98	$152.00	$152.00
Purchase #2	$89.44	9.502%	$97.9386	$97.94	$97.95	$97.90
Purchase #3	$197.53	5.484%	$208.3625	$208.36	$208.35	$208.40
Purchase #4	$238.88	10.559%	$264.1033	$264.10	$264.10	$264.10
Purchase #5	$166.59	3.419%	$172.2857	$172.29	$172.30	$172.30
Purchase #6	$21.72	4.140%	$22.6192	$22.62	$22.60	$22.60
Purchase #7	$10.95	3.163%	$11.2963	$11.30	$11.30	$11.30
7 purchase totals =	$859.01		$928.5875	$928.59	$928.60	$928.60