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	$179.75	3.334%	$185.7429	$185.74	$185.75	$185.70
Purchase #2	$52.74	13.106%	$59.6521	$59.65	$59.65	$59.70
Purchase #3	$111.48	5.411%	$117.5122	$117.51	$117.50	$117.50
Purchase #4	$48.90	3.679%	$50.699	$50.70	$50.70	$50.70
Purchase #5	$64.90	9.743%	$71.2232	$71.22	$71.20	$71.20
Purchase #6	$11.65	13.610%	$13.2356	$13.24	$13.25	$13.20
Purchase #7	$104.46	12.418%	$117.4318	$117.43	$117.45	$117.40
7 purchase totals =	$573.88		$615.4968	$615.49	$615.50	$615.40