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	$43.41	4.651%	$45.429	$45.43	$45.45	$45.40
Purchase #2	$57.42	8.771%	$62.4563	$62.46	$62.45	$62.50
Purchase #3	$244.73	11.214%	$272.174	$272.17	$272.15	$272.20
Purchase #4	$30.82	7.583%	$33.1571	$33.16	$33.15	$33.20
Purchase #5	$233.91	9.245%	$255.535	$255.54	$255.55	$255.50
Purchase #6	$14.70	5.494%	$15.5076	$15.51	$15.50	$15.50
Purchase #7	$239.89	9.874%	$263.5767	$263.58	$263.60	$263.60
7 purchase totals =	$864.88		$947.8357	$947.85	$947.85	$947.90