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	$213.48	4.501%	$223.0887	$223.09	$223.10	$223.10
Purchase #2	$72.42	6.476%	$77.1099	$77.11	$77.10	$77.10
Purchase #3	$158.38	10.693%	$175.3156	$175.32	$175.30	$175.30
Purchase #4	$78.70	13.476%	$89.3056	$89.31	$89.30	$89.30
Purchase #5	$91.37	9.416%	$99.9734	$99.97	$99.95	$100.00
Purchase #6	$172.68	9.537%	$189.1485	$189.15	$189.15	$189.10
Purchase #7	$60.29	10.747%	$66.7694	$66.77	$66.75	$66.80
7 purchase totals =	$847.32		$920.7111	$920.72	$920.65	$920.70