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	$133.39	13.719%	$151.6898	$151.69	$151.70	$151.70
Purchase #2	$246.47	3.290%	$254.5789	$254.58	$254.60	$254.60
Purchase #3	$10.72	9.389%	$11.7265	$11.73	$11.75	$11.70
Purchase #4	$53.73	3.683%	$55.7089	$55.71	$55.70	$55.70
Purchase #5	$126.74	5.587%	$133.821	$133.82	$133.80	$133.80
Purchase #6	$196.65	8.577%	$213.5167	$213.52	$213.50	$213.50
Purchase #7	$248.48	12.378%	$279.2369	$279.24	$279.25	$279.20
7 purchase totals =	$1,016.18		$1,100.2787	$1,100.29	$1,100.30	$1,100.20