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	$100.34	10.505%	$110.8807	$110.88	$110.90	$110.90
Purchase #2	$87.36	11.397%	$97.3164	$97.32	$97.30	$97.30
Purchase #3	$90.53	4.256%	$94.383	$94.38	$94.40	$94.40
Purchase #4	$22.52	12.479%	$25.3303	$25.33	$25.35	$25.30
Purchase #5	$235.58	8.737%	$256.1626	$256.16	$256.15	$256.20
Purchase #6	$74.65	5.587%	$78.8207	$78.82	$78.80	$78.80
Purchase #7	$110.38	12.371%	$124.0351	$124.04	$124.05	$124.00
7 purchase totals =	$721.36		$786.9288	$786.93	$786.95	$786.90