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	$208.95	7.784%	$225.2147	$225.21	$225.20	$225.20
Purchase #2	$87.72	3.346%	$90.6551	$90.66	$90.65	$90.70
Purchase #3	$66.71	10.390%	$73.6412	$73.64	$73.65	$73.60
Purchase #4	$250.91	5.419%	$264.5068	$264.51	$264.50	$264.50
Purchase #5	$214.89	3.791%	$223.0365	$223.04	$223.05	$223.00
Purchase #6	$53.94	4.600%	$56.4212	$56.42	$56.40	$56.40
Purchase #7	$119.28	8.624%	$129.5667	$129.57	$129.55	$129.60
7 purchase totals =	$1,002.40		$1,063.0422	$1,063.05	$1,063.00	$1,063.00