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	$55.58	11.320%	$61.8717	$61.87	$61.85	$61.90
Purchase #2	$62.75	4.344%	$65.4759	$65.48	$65.50	$65.50
Purchase #3	$94.32	8.235%	$102.0873	$102.09	$102.10	$102.10
Purchase #4	$88.52	12.785%	$99.8373	$99.84	$99.85	$99.80
Purchase #5	$121.89	5.201%	$128.2295	$128.23	$128.25	$128.20
Purchase #6	$14.53	6.224%	$15.4343	$15.43	$15.45	$15.40
Purchase #7	$29.45	7.672%	$31.7094	$31.71	$31.70	$31.70
7 purchase totals =	$467.04		$504.6454	$504.65	$504.70	$504.60