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	$140.93	3.838%	$146.3389	$146.34	$146.35	$146.30
Purchase #2	$58.87	13.289%	$66.6932	$66.69	$66.70	$66.70
Purchase #3	$21.29	4.807%	$22.3134	$22.31	$22.30	$22.30
Purchase #4	$130.34	12.652%	$146.8306	$146.83	$146.85	$146.80
Purchase #5	$10.75	3.389%	$11.1143	$11.11	$11.10	$11.10
Purchase #6	$111.78	10.552%	$123.575	$123.58	$123.60	$123.60
Purchase #7	$248.92	7.451%	$267.467	$267.47	$267.45	$267.50
7 purchase totals =	$722.88		$784.3324	$784.33	$784.35	$784.30