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	$126.82	8.401%	$137.4741	$137.47	$137.45	$137.50
Purchase #2	$226.91	11.735%	$253.5379	$253.54	$253.55	$253.50
Purchase #3	$130.51	7.762%	$140.6402	$140.64	$140.65	$140.60
Purchase #4	$94.66	11.448%	$105.4967	$105.50	$105.50	$105.50
Purchase #5	$114.43	10.512%	$126.4589	$126.46	$126.45	$126.50
Purchase #6	$43.34	11.129%	$48.1633	$48.16	$48.15	$48.20
Purchase #7	$11.55	8.602%	$12.5435	$12.54	$12.55	$12.50
7 purchase totals =	$748.22		$824.3146	$824.31	$824.30	$824.30