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	$172.47	4.462%	$180.1656	$180.17	$180.15	$180.20
Purchase #2	$18.74	11.605%	$20.9148	$20.91	$20.90	$20.90
Purchase #3	$160.85	8.218%	$174.0687	$174.07	$174.05	$174.10
Purchase #4	$248.48	10.118%	$273.6212	$273.62	$273.60	$273.60
Purchase #5	$37.37	5.659%	$39.4848	$39.48	$39.50	$39.50
Purchase #6	$247.85	12.836%	$279.664	$279.66	$279.65	$279.70
Purchase #7	$67.25	7.192%	$72.0866	$72.09	$72.10	$72.10
7 purchase totals =	$953.01		$1,040.0057	$1,040.00	$1,039.95	$1,040.10