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	$187.69	4.685%	$196.4833	$196.48	$196.50	$196.50
Purchase #2	$175.39	7.680%	$188.86	$188.86	$188.85	$188.90
Purchase #3	$210.50	6.323%	$223.8099	$223.81	$223.80	$223.80
Purchase #4	$77.75	13.147%	$87.9718	$87.97	$87.95	$88.00
Purchase #5	$18.71	11.313%	$20.8267	$20.83	$20.85	$20.80
Purchase #6	$197.30	13.601%	$224.1348	$224.13	$224.15	$224.10
Purchase #7	$109.53	10.643%	$121.1873	$121.19	$121.20	$121.20
7 purchase totals =	$976.87		$1,063.2738	$1,063.27	$1,063.30	$1,063.30