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	$85.70	9.554%	$93.8878	$93.89	$93.90	$93.90
Purchase #2	$166.59	5.380%	$175.5525	$175.55	$175.55	$175.60
Purchase #3	$154.32	13.777%	$175.5807	$175.58	$175.60	$175.60
Purchase #4	$87.89	13.102%	$99.4053	$99.41	$99.40	$99.40
Purchase #5	$75.49	10.411%	$83.3493	$83.35	$83.35	$83.30
Purchase #6	$134.54	13.811%	$153.1213	$153.12	$153.10	$153.10
Purchase #7	$93.34	13.335%	$105.7869	$105.79	$105.80	$105.80
7 purchase totals =	$797.87		$886.6838	$886.69	$886.70	$886.70