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	$238.56	12.820%	$269.1434	$269.14	$269.15	$269.10
Purchase #2	$29.34	4.141%	$30.555	$30.56	$30.55	$30.60
Purchase #3	$150.34	12.494%	$169.1235	$169.12	$169.10	$169.10
Purchase #4	$58.45	13.553%	$66.3717	$66.37	$66.35	$66.40
Purchase #5	$208.92	9.860%	$229.5195	$229.52	$229.50	$229.50
Purchase #6	$235.85	7.826%	$254.3076	$254.31	$254.30	$254.30
Purchase #7	$127.77	3.404%	$132.1193	$132.12	$132.10	$132.10
7 purchase totals =	$1,049.23		$1,151.1400	$1,151.14	$1,151.05	$1,151.10