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	$12.33	7.521%	$13.2573	$13.26	$13.25	$13.30
Purchase #2	$53.26	11.634%	$59.4563	$59.46	$59.45	$59.50
Purchase #3	$195.62	7.363%	$210.0235	$210.02	$210.00	$210.00
Purchase #4	$90.56	10.262%	$99.8533	$99.85	$99.85	$99.90
Purchase #5	$9.80	9.140%	$10.6957	$10.70	$10.70	$10.70
Purchase #6	$59.37	12.221%	$66.6256	$66.63	$66.65	$66.60
Purchase #7	$188.80	7.538%	$203.0317	$203.03	$203.05	$203.00
7 purchase totals =	$609.74		$662.9434	$662.95	$662.95	$663.00