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	$224.35	11.142%	$249.3471	$249.35	$249.35	$249.30
Purchase #2	$202.42	6.429%	$215.4336	$215.43	$215.45	$215.40
Purchase #3	$89.77	6.327%	$95.4497	$95.45	$95.45	$95.40
Purchase #4	$116.51	13.205%	$131.8951	$131.90	$131.90	$131.90
Purchase #5	$148.31	7.321%	$159.1678	$159.17	$159.15	$159.20
Purchase #6	$244.72	3.599%	$253.5275	$253.53	$253.55	$253.50
Purchase #7	$159.30	12.376%	$179.015	$179.02	$179.00	$179.00
7 purchase totals =	$1,185.38		$1,283.8358	$1,283.85	$1,283.85	$1,283.70