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	$202.67	6.805%	$216.4617	$216.46	$216.45	$216.50
Purchase #2	$213.55	9.379%	$233.5789	$233.58	$233.60	$233.60
Purchase #3	$230.68	7.635%	$248.2924	$248.29	$248.30	$248.30
Purchase #4	$103.37	7.484%	$111.1062	$111.11	$111.10	$111.10
Purchase #5	$98.84	12.576%	$111.2701	$111.27	$111.25	$111.30
Purchase #6	$82.77	12.186%	$92.8564	$92.86	$92.85	$92.90
Purchase #7	$203.94	3.733%	$211.5531	$211.55	$211.55	$211.60
7 purchase totals =	$1,135.82		$1,225.1188	$1,225.12	$1,225.10	$1,225.30