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	$247.45	6.577%	$263.7248	$263.72	$263.70	$263.70
Purchase #2	$237.62	11.300%	$264.4711	$264.47	$264.45	$264.50
Purchase #3	$199.95	9.283%	$218.5114	$218.51	$218.50	$218.50
Purchase #4	$61.38	5.262%	$64.6098	$64.61	$64.60	$64.60
Purchase #5	$120.33	8.350%	$130.3776	$130.38	$130.40	$130.40
Purchase #6	$141.90	9.305%	$155.1038	$155.10	$155.10	$155.10
Purchase #7	$55.34	10.868%	$61.3544	$61.35	$61.35	$61.40
7 purchase totals =	$1,063.97		$1,158.1529	$1,158.14	$1,158.10	$1,158.20