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	$177.39	8.156%	$191.8579	$191.86	$191.85	$191.90
Purchase #2	$67.77	11.238%	$75.386	$75.39	$75.40	$75.40
Purchase #3	$208.66	10.641%	$230.8635	$230.86	$230.85	$230.90
Purchase #4	$222.43	11.842%	$248.7702	$248.77	$248.75	$248.80
Purchase #5	$125.37	9.319%	$137.0532	$137.05	$137.05	$137.10
Purchase #6	$74.56	4.737%	$78.0919	$78.09	$78.10	$78.10
Purchase #7	$131.51	11.641%	$146.8191	$146.82	$146.80	$146.80
7 purchase totals =	$1,007.69		$1,108.8418	$1,108.84	$1,108.80	$1,109.00