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	$100.90	10.429%	$111.4229	$111.42	$111.40	$111.40
Purchase #2	$244.53	4.728%	$256.0914	$256.09	$256.10	$256.10
Purchase #3	$163.46	12.758%	$184.3142	$184.31	$184.30	$184.30
Purchase #4	$31.77	4.738%	$33.2753	$33.28	$33.30	$33.30
Purchase #5	$146.80	3.492%	$151.9263	$151.93	$151.95	$151.90
Purchase #6	$135.29	10.455%	$149.4346	$149.43	$149.45	$149.40
Purchase #7	$128.69	13.281%	$145.7813	$145.78	$145.80	$145.80
7 purchase totals =	$951.44		$1,032.2460	$1,032.24	$1,032.30	$1,032.20