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	$39.38	11.184%	$43.7843	$43.78	$43.80	$43.80
Purchase #2	$176.58	4.547%	$184.6091	$184.61	$184.60	$184.60
Purchase #3	$11.25	7.784%	$12.1257	$12.13	$12.15	$12.10
Purchase #4	$32.95	11.843%	$36.8523	$36.85	$36.85	$36.90
Purchase #5	$203.77	7.648%	$219.3543	$219.35	$219.35	$219.40
Purchase #6	$48.61	10.713%	$53.8176	$53.82	$53.80	$53.80
Purchase #7	$49.53	12.733%	$55.8367	$55.84	$55.85	$55.80
7 purchase totals =	$562.07		$606.3800	$606.38	$606.40	$606.40