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	$111.48	4.362%	$116.3428	$116.34	$116.35	$116.30
Purchase #2	$92.61	8.137%	$100.1457	$100.15	$100.15	$100.10
Purchase #3	$102.47	13.411%	$116.2123	$116.21	$116.20	$116.20
Purchase #4	$157.76	4.824%	$165.3703	$165.37	$165.35	$165.40
Purchase #5	$152.75	9.706%	$167.5759	$167.58	$167.60	$167.60
Purchase #6	$64.45	10.821%	$71.4241	$71.42	$71.40	$71.40
Purchase #7	$38.35	4.487%	$40.0708	$40.07	$40.05	$40.10
7 purchase totals =	$719.87		$777.1419	$777.14	$777.10	$777.10