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	$235.65	12.244%	$264.503	$264.50	$264.50	$264.50
Purchase #2	$202.53	11.260%	$225.3349	$225.33	$225.35	$225.30
Purchase #3	$93.88	13.348%	$106.4111	$106.41	$106.40	$106.40
Purchase #4	$93.47	10.237%	$103.0385	$103.04	$103.05	$103.00
Purchase #5	$37.29	8.473%	$40.4496	$40.45	$40.45	$40.40
Purchase #6	$228.51	5.844%	$241.8641	$241.86	$241.85	$241.90
Purchase #7	$113.69	8.777%	$123.6686	$123.67	$123.65	$123.70
7 purchase totals =	$1,005.02		$1,105.2698	$1,105.26	$1,105.25	$1,105.20