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	$42.44	7.794%	$45.7478	$45.75	$45.75	$45.70
Purchase #2	$15.47	9.212%	$16.8951	$16.90	$16.90	$16.90
Purchase #3	$165.62	4.289%	$172.7234	$172.72	$172.70	$172.70
Purchase #4	$102.38	9.111%	$111.7078	$111.71	$111.70	$111.70
Purchase #5	$211.52	5.345%	$222.8257	$222.83	$222.85	$222.80
Purchase #6	$39.75	5.220%	$41.825	$41.83	$41.85	$41.80
Purchase #7	$54.58	11.699%	$60.9653	$60.97	$60.95	$61.00
7 purchase totals =	$631.76		$672.6901	$672.71	$672.70	$672.60