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	$130.64	12.148%	$146.5101	$146.51	$146.50	$146.50
Purchase #2	$95.94	3.323%	$99.1281	$99.13	$99.15	$99.10
Purchase #3	$231.71	5.631%	$244.7576	$244.76	$244.75	$244.80
Purchase #4	$95.91	4.614%	$100.3353	$100.34	$100.35	$100.30
Purchase #5	$233.90	11.199%	$260.0945	$260.09	$260.10	$260.10
Purchase #6	$33.29	13.844%	$37.8987	$37.90	$37.90	$37.90
Purchase #7	$139.42	5.245%	$146.7326	$146.73	$146.75	$146.70
7 purchase totals =	$960.81		$1,035.4569	$1,035.46	$1,035.50	$1,035.40