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	$172.94	10.178%	$190.5418	$190.54	$190.55	$190.50
Purchase #2	$78.51	12.217%	$88.1016	$88.10	$88.10	$88.10
Purchase #3	$92.45	4.149%	$96.2858	$96.29	$96.30	$96.30
Purchase #4	$10.25	7.769%	$11.0463	$11.05	$11.05	$11.00
Purchase #5	$125.83	9.461%	$137.7348	$137.73	$137.75	$137.70
Purchase #6	$55.87	3.629%	$57.8975	$57.90	$57.90	$57.90
Purchase #7	$213.63	5.533%	$225.4501	$225.45	$225.45	$225.50
7 purchase totals =	$749.48		$807.0579	$807.06	$807.10	$807.00