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	$136.76	11.653%	$152.6966	$152.70	$152.70	$152.70
Purchase #2	$186.67	10.626%	$206.5056	$206.51	$206.50	$206.50
Purchase #3	$45.29	6.639%	$48.2968	$48.30	$48.30	$48.30
Purchase #4	$119.29	5.769%	$126.1718	$126.17	$126.15	$126.20
Purchase #5	$49.94	12.716%	$56.2904	$56.29	$56.30	$56.30
Purchase #6	$60.31	10.226%	$66.4773	$66.48	$66.50	$66.50
Purchase #7	$12.47	3.334%	$12.8857	$12.89	$12.90	$12.90
7 purchase totals =	$610.73		$669.3242	$669.34	$669.35	$669.40