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	$136.48	10.799%	$151.2185	$151.22	$151.20	$151.20
Purchase #2	$135.78	4.874%	$142.3979	$142.40	$142.40	$142.40
Purchase #3	$139.35	5.164%	$146.546	$146.55	$146.55	$146.50
Purchase #4	$66.82	8.634%	$72.5892	$72.59	$72.60	$72.60
Purchase #5	$12.92	6.556%	$13.767	$13.77	$13.75	$13.80
Purchase #6	$248.76	11.449%	$277.2405	$277.24	$277.25	$277.20
Purchase #7	$64.49	4.449%	$67.3592	$67.36	$67.35	$67.40
7 purchase totals =	$804.60		$871.1183	$871.13	$871.10	$871.10