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	$150.50	3.447%	$155.6877	$155.69	$155.70	$155.70
Purchase #2	$127.69	7.730%	$137.5604	$137.56	$137.55	$137.60
Purchase #3	$31.80	8.867%	$34.6197	$34.62	$34.60	$34.60
Purchase #4	$130.27	13.863%	$148.3293	$148.33	$148.35	$148.30
Purchase #5	$72.53	13.256%	$82.1446	$82.14	$82.15	$82.10
Purchase #6	$189.91	9.869%	$208.6522	$208.65	$208.65	$208.70
Purchase #7	$152.36	3.817%	$158.1756	$158.18	$158.20	$158.20
7 purchase totals =	$855.06		$925.1695	$925.17	$925.20	$925.20