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	$40.92	10.345%	$45.1532	$45.15	$45.15	$45.20
Purchase #2	$194.56	13.129%	$220.1038	$220.10	$220.10	$220.10
Purchase #3	$56.75	4.629%	$59.377	$59.38	$59.40	$59.40
Purchase #4	$133.82	10.846%	$148.3341	$148.33	$148.35	$148.30
Purchase #5	$20.37	8.343%	$22.0695	$22.07	$22.05	$22.10
Purchase #6	$101.75	9.533%	$111.4498	$111.45	$111.45	$111.40
Purchase #7	$83.41	8.451%	$90.459	$90.46	$90.45	$90.50
7 purchase totals =	$631.58		$696.9464	$696.94	$696.95	$697.00