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	$65.45	10.502%	$72.3236	$72.32	$72.30	$72.30
Purchase #2	$133.41	13.777%	$151.7899	$151.79	$151.80	$151.80
Purchase #3	$91.57	5.363%	$96.4809	$96.48	$96.50	$96.50
Purchase #4	$15.77	11.233%	$17.5414	$17.54	$17.55	$17.50
Purchase #5	$61.67	5.208%	$64.8818	$64.88	$64.90	$64.90
Purchase #6	$66.67	6.711%	$71.1442	$71.14	$71.15	$71.10
Purchase #7	$52.97	9.824%	$58.1738	$58.17	$58.15	$58.20
7 purchase totals =	$487.51		$532.3356	$532.32	$532.35	$532.30