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	$56.40	7.224%	$60.4743	$60.47	$60.45	$60.50
Purchase #2	$23.94	3.252%	$24.7185	$24.72	$24.70	$24.70
Purchase #3	$135.45	13.598%	$153.8685	$153.87	$153.85	$153.90
Purchase #4	$95.68	4.337%	$99.8296	$99.83	$99.85	$99.80
Purchase #5	$121.82	7.655%	$131.1453	$131.15	$131.15	$131.10
Purchase #6	$102.52	11.361%	$114.1673	$114.17	$114.15	$114.20
Purchase #7	$174.40	4.637%	$182.4869	$182.49	$182.50	$182.50
7 purchase totals =	$710.21		$766.6904	$766.70	$766.65	$766.70