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	$213.54	3.530%	$221.078	$221.08	$221.10	$221.10
Purchase #2	$137.77	4.626%	$144.1432	$144.14	$144.15	$144.10
Purchase #3	$27.50	5.261%	$28.9468	$28.95	$28.95	$28.90
Purchase #4	$43.39	6.131%	$46.0502	$46.05	$46.05	$46.10
Purchase #5	$206.85	3.526%	$214.1435	$214.14	$214.15	$214.10
Purchase #6	$82.82	13.157%	$93.7166	$93.72	$93.70	$93.70
Purchase #7	$225.31	13.238%	$255.1365	$255.14	$255.15	$255.10
7 purchase totals =	$937.18		$1,003.2148	$1,003.22	$1,003.25	$1,003.10