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	$133.51	13.126%	$151.0345	$151.03	$151.05	$151.00
Purchase #2	$248.38	4.229%	$258.884	$258.88	$258.90	$258.90
Purchase #3	$63.70	13.224%	$72.1237	$72.12	$72.10	$72.10
Purchase #4	$199.25	11.467%	$222.098	$222.10	$222.10	$222.10
Purchase #5	$106.56	11.433%	$118.743	$118.74	$118.75	$118.70
Purchase #6	$11.67	9.662%	$12.7976	$12.80	$12.80	$12.80
Purchase #7	$230.83	5.433%	$243.371	$243.37	$243.35	$243.40
7 purchase totals =	$993.90		$1,079.0518	$1,079.04	$1,079.05	$1,079.00