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	$53.68	11.200%	$59.6922	$59.69	$59.70	$59.70
Purchase #2	$203.70	7.451%	$218.8777	$218.88	$218.90	$218.90
Purchase #3	$166.35	4.560%	$173.9356	$173.94	$173.95	$173.90
Purchase #4	$25.61	6.110%	$27.1748	$27.17	$27.15	$27.20
Purchase #5	$121.43	4.675%	$127.1069	$127.11	$127.10	$127.10
Purchase #6	$81.53	8.213%	$88.2261	$88.23	$88.25	$88.20
Purchase #7	$92.71	8.368%	$100.468	$100.47	$100.45	$100.50
7 purchase totals =	$745.01		$795.4813	$795.49	$795.50	$795.50