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	$65.94	9.366%	$72.1159	$72.12	$72.10	$72.10
Purchase #2	$32.91	13.593%	$37.3835	$37.38	$37.40	$37.40
Purchase #3	$240.83	9.108%	$262.7648	$262.76	$262.75	$262.80
Purchase #4	$151.80	13.849%	$172.8228	$172.82	$172.80	$172.80
Purchase #5	$43.41	5.324%	$45.7211	$45.72	$45.70	$45.70
Purchase #6	$223.79	11.583%	$249.7116	$249.71	$249.70	$249.70
Purchase #7	$49.75	10.717%	$55.0817	$55.08	$55.10	$55.10
7 purchase totals =	$808.43		$895.6014	$895.59	$895.55	$895.60