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	$235.30	6.541%	$250.691	$250.69	$250.70	$250.70
Purchase #2	$229.41	11.425%	$255.6201	$255.62	$255.60	$255.60
Purchase #3	$118.52	10.208%	$130.6185	$130.62	$130.60	$130.60
Purchase #4	$52.86	4.322%	$55.1446	$55.14	$55.15	$55.10
Purchase #5	$68.86	3.805%	$71.4801	$71.48	$71.50	$71.50
Purchase #6	$17.38	3.140%	$17.9257	$17.93	$17.95	$17.90
Purchase #7	$40.94	10.795%	$45.3595	$45.36	$45.35	$45.40
7 purchase totals =	$763.27		$826.8395	$826.84	$826.85	$826.80