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	$68.54	4.346%	$71.5187	$71.52	$71.50	$71.50
Purchase #2	$90.43	10.453%	$99.8826	$99.88	$99.90	$99.90
Purchase #3	$158.52	13.861%	$180.4925	$180.49	$180.50	$180.50
Purchase #4	$130.86	13.707%	$148.797	$148.80	$148.80	$148.80
Purchase #5	$45.80	3.464%	$47.3865	$47.39	$47.40	$47.40
Purchase #6	$57.41	4.600%	$60.0509	$60.05	$60.05	$60.10
Purchase #7	$125.89	3.247%	$129.9776	$129.98	$130.00	$130.00
7 purchase totals =	$677.45		$738.1058	$738.11	$738.15	$738.20