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	$60.83	10.231%	$67.0535	$67.05	$67.05	$67.10
Purchase #2	$30.34	7.142%	$32.5069	$32.51	$32.50	$32.50
Purchase #3	$155.32	11.175%	$172.677	$172.68	$172.70	$172.70
Purchase #4	$152.55	8.666%	$165.77	$165.77	$165.75	$165.80
Purchase #5	$223.95	11.565%	$249.8498	$249.85	$249.85	$249.80
Purchase #6	$238.27	7.142%	$255.2872	$255.29	$255.30	$255.30
Purchase #7	$95.44	11.691%	$106.5979	$106.60	$106.60	$106.60
7 purchase totals =	$956.70		$1,049.7423	$1,049.75	$1,049.75	$1,049.80