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	$149.31	5.242%	$157.1368	$157.14	$157.15	$157.10
Purchase #2	$64.92	10.479%	$71.723	$71.72	$71.70	$71.70
Purchase #3	$140.84	11.570%	$157.1352	$157.14	$157.15	$157.10
Purchase #4	$154.82	8.662%	$168.2305	$168.23	$168.25	$168.20
Purchase #5	$10.32	8.235%	$11.1699	$11.17	$11.15	$11.20
Purchase #6	$155.71	7.589%	$167.5268	$167.53	$167.55	$167.50
Purchase #7	$238.90	6.830%	$255.2169	$255.22	$255.20	$255.20
7 purchase totals =	$914.82		$988.1391	$988.15	$988.15	$988.00