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	$213.53	12.172%	$239.5209	$239.52	$239.50	$239.50
Purchase #2	$194.59	8.678%	$211.4765	$211.48	$211.50	$211.50
Purchase #3	$60.48	10.599%	$66.8903	$66.89	$66.90	$66.90
Purchase #4	$132.71	13.318%	$150.3843	$150.38	$150.40	$150.40
Purchase #5	$48.48	11.620%	$54.1134	$54.11	$54.10	$54.10
Purchase #6	$42.39	5.386%	$44.6731	$44.67	$44.65	$44.70
Purchase #7	$221.73	9.634%	$243.0915	$243.09	$243.10	$243.10
7 purchase totals =	$913.91		$1,010.1500	$1,010.14	$1,010.15	$1,010.20