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	$75.63	13.245%	$85.6472	$85.65	$85.65	$85.60
Purchase #2	$120.98	13.773%	$137.6426	$137.64	$137.65	$137.60
Purchase #3	$53.31	4.656%	$55.7921	$55.79	$55.80	$55.80
Purchase #4	$121.57	4.118%	$126.5763	$126.58	$126.60	$126.60
Purchase #5	$185.64	11.244%	$206.5134	$206.51	$206.50	$206.50
Purchase #6	$229.33	11.695%	$256.1501	$256.15	$256.15	$256.20
Purchase #7	$28.73	13.504%	$32.6097	$32.61	$32.60	$32.60
7 purchase totals =	$815.19		$900.9314	$900.93	$900.95	$900.90