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	$82.31	10.494%	$90.9476	$90.95	$90.95	$90.90
Purchase #2	$105.33	4.213%	$109.7676	$109.77	$109.75	$109.80
Purchase #3	$19.48	8.468%	$21.1296	$21.13	$21.15	$21.10
Purchase #4	$11.94	10.414%	$13.1834	$13.18	$13.20	$13.20
Purchase #5	$6.97	13.245%	$7.8932	$7.89	$7.90	$7.90
Purchase #6	$70.25	6.672%	$74.9371	$74.94	$74.95	$74.90
Purchase #7	$26.34	9.608%	$28.8707	$28.87	$28.85	$28.90
7 purchase totals =	$322.62		$346.7292	$346.73	$346.75	$346.70