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	$80.56	3.555%	$83.4239	$83.42	$83.40	$83.40
Purchase #2	$137.70	11.227%	$153.1596	$153.16	$153.15	$153.20
Purchase #3	$223.29	4.324%	$232.9451	$232.95	$232.95	$232.90
Purchase #4	$108.27	13.200%	$122.5616	$122.56	$122.55	$122.60
Purchase #5	$107.94	7.631%	$116.1769	$116.18	$116.20	$116.20
Purchase #6	$175.72	8.267%	$190.2468	$190.25	$190.25	$190.20
Purchase #7	$143.54	13.222%	$162.5189	$162.52	$162.50	$162.50
7 purchase totals =	$977.02		$1,061.0328	$1,061.04	$1,061.00	$1,061.00