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	$221.34	5.467%	$233.4407	$233.44	$233.45	$233.40
Purchase #2	$135.62	4.392%	$141.5764	$141.58	$141.60	$141.60
Purchase #3	$78.54	12.213%	$88.1321	$88.13	$88.15	$88.10
Purchase #4	$138.27	5.699%	$146.15	$146.15	$146.15	$146.20
Purchase #5	$157.41	4.758%	$164.8996	$164.90	$164.90	$164.90
Purchase #6	$230.69	10.777%	$255.5515	$255.55	$255.55	$255.60
Purchase #7	$244.82	7.584%	$263.3871	$263.39	$263.40	$263.40
7 purchase totals =	$1,206.69		$1,293.1374	$1,293.14	$1,293.20	$1,293.20