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	$40.69	12.506%	$45.7787	$45.78	$45.80	$45.80
Purchase #2	$165.52	3.554%	$171.4026	$171.40	$171.40	$171.40
Purchase #3	$130.75	9.590%	$143.2889	$143.29	$143.30	$143.30
Purchase #4	$31.65	9.527%	$34.6653	$34.67	$34.65	$34.70
Purchase #5	$95.98	9.848%	$105.4321	$105.43	$105.45	$105.40
Purchase #6	$123.62	13.664%	$140.5114	$140.51	$140.50	$140.50
Purchase #7	$118.45	6.259%	$125.8638	$125.86	$125.85	$125.90
7 purchase totals =	$706.66		$766.9428	$766.94	$766.95	$767.00