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	$116.60	13.143%	$131.9247	$131.92	$131.90	$131.90
Purchase #2	$42.82	8.732%	$46.559	$46.56	$46.55	$46.60
Purchase #3	$243.25	5.797%	$257.3512	$257.35	$257.35	$257.40
Purchase #4	$90.71	8.186%	$98.1355	$98.14	$98.15	$98.10
Purchase #5	$32.96	12.420%	$37.0536	$37.05	$37.05	$37.10
Purchase #6	$218.38	5.298%	$229.9498	$229.95	$229.95	$229.90
Purchase #7	$68.31	9.105%	$74.5296	$74.53	$74.55	$74.50
7 purchase totals =	$813.03		$875.5034	$875.50	$875.50	$875.50