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	$91.39	5.300%	$96.2337	$96.23	$96.25	$96.20
Purchase #2	$34.60	9.576%	$37.9133	$37.91	$37.90	$37.90
Purchase #3	$57.99	11.430%	$64.6183	$64.62	$64.60	$64.60
Purchase #4	$58.27	5.492%	$61.4702	$61.47	$61.45	$61.50
Purchase #5	$140.65	4.568%	$147.0749	$147.07	$147.05	$147.10
Purchase #6	$81.95	11.276%	$91.1907	$91.19	$91.20	$91.20
Purchase #7	$106.60	4.804%	$111.7211	$111.72	$111.70	$111.70
7 purchase totals =	$571.45		$610.2222	$610.21	$610.15	$610.20