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	$94.96	12.481%	$106.812	$106.81	$106.80	$106.80
Purchase #2	$76.74	11.874%	$85.8521	$85.85	$85.85	$85.90
Purchase #3	$15.95	5.197%	$16.7789	$16.78	$16.80	$16.80
Purchase #4	$83.48	7.194%	$89.4856	$89.49	$89.50	$89.50
Purchase #5	$94.92	7.639%	$102.1709	$102.17	$102.15	$102.20
Purchase #6	$34.51	7.324%	$37.0375	$37.04	$37.05	$37.00
Purchase #7	$42.83	6.688%	$45.6945	$45.69	$45.70	$45.70
7 purchase totals =	$443.39		$483.8315	$483.83	$483.85	$483.90