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	$44.80	4.521%	$46.8254	$46.83	$46.85	$46.80
Purchase #2	$154.54	7.500%	$166.1305	$166.13	$166.15	$166.10
Purchase #3	$124.50	11.657%	$139.013	$139.01	$139.00	$139.00
Purchase #4	$191.46	3.129%	$197.4508	$197.45	$197.45	$197.50
Purchase #5	$34.47	8.713%	$37.4734	$37.47	$37.45	$37.50
Purchase #6	$125.58	12.191%	$140.8895	$140.89	$140.90	$140.90
Purchase #7	$29.77	6.175%	$31.6083	$31.61	$31.60	$31.60
7 purchase totals =	$705.12		$759.3909	$759.39	$759.40	$759.40