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	$50.57	7.718%	$54.473	$54.47	$54.45	$54.50
Purchase #2	$48.67	10.309%	$53.6874	$53.69	$53.70	$53.70
Purchase #3	$55.81	7.728%	$60.123	$60.12	$60.10	$60.10
Purchase #4	$10.57	8.188%	$11.4355	$11.44	$11.45	$11.40
Purchase #5	$128.50	13.741%	$146.1572	$146.16	$146.15	$146.20
Purchase #6	$106.45	6.380%	$113.2415	$113.24	$113.25	$113.20
Purchase #7	$236.75	9.351%	$258.8885	$258.89	$258.90	$258.90
7 purchase totals =	$637.32		$698.0061	$698.01	$698.00	$698.00