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	$125.32	7.569%	$134.8055	$134.81	$134.80	$134.80
Purchase #2	$235.81	7.494%	$253.4816	$253.48	$253.50	$253.50
Purchase #3	$230.91	10.269%	$254.6221	$254.62	$254.60	$254.60
Purchase #4	$231.57	12.231%	$259.8933	$259.89	$259.90	$259.90
Purchase #5	$165.25	5.228%	$173.8893	$173.89	$173.90	$173.90
Purchase #6	$84.83	9.476%	$92.8685	$92.87	$92.85	$92.90
Purchase #7	$95.69	10.507%	$105.7441	$105.74	$105.75	$105.70
7 purchase totals =	$1,169.38		$1,275.3044	$1,275.30	$1,275.30	$1,275.30