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	$94.86	10.600%	$104.9152	$104.92	$104.90	$104.90
Purchase #2	$230.94	5.664%	$244.0204	$244.02	$244.00	$244.00
Purchase #3	$72.25	11.634%	$80.6556	$80.66	$80.65	$80.70
Purchase #4	$94.32	11.653%	$105.3111	$105.31	$105.30	$105.30
Purchase #5	$10.70	8.258%	$11.5836	$11.58	$11.60	$11.60
Purchase #6	$212.29	13.300%	$240.5246	$240.52	$240.50	$240.50
Purchase #7	$109.74	12.174%	$123.0997	$123.10	$123.10	$123.10
7 purchase totals =	$825.10		$910.1102	$910.11	$910.05	$910.10