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	$48.61	7.648%	$52.3277	$52.33	$52.35	$52.30
Purchase #2	$28.78	12.182%	$32.286	$32.29	$32.30	$32.30
Purchase #3	$36.78	12.719%	$41.458	$41.46	$41.45	$41.50
Purchase #4	$18.26	12.180%	$20.4841	$20.48	$20.50	$20.50
Purchase #5	$246.43	9.536%	$269.9296	$269.93	$269.95	$269.90
Purchase #6	$43.68	3.141%	$45.052	$45.05	$45.05	$45.10
Purchase #7	$40.94	7.293%	$43.9258	$43.93	$43.95	$43.90
7 purchase totals =	$463.48		$505.4632	$505.47	$505.55	$505.50