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	$247.59	3.452%	$256.1368	$256.14	$256.15	$256.10
Purchase #2	$50.85	7.522%	$54.6749	$54.67	$54.65	$54.70
Purchase #3	$218.58	4.176%	$227.7079	$227.71	$227.70	$227.70
Purchase #4	$187.96	11.267%	$209.1375	$209.14	$209.15	$209.10
Purchase #5	$238.73	8.672%	$259.4327	$259.43	$259.45	$259.40
Purchase #6	$43.45	11.256%	$48.3407	$48.34	$48.35	$48.30
Purchase #7	$5.42	9.278%	$5.9229	$5.92	$5.90	$5.90
7 purchase totals =	$992.58		$1,061.3534	$1,061.35	$1,061.35	$1,061.20