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	$58.77	8.315%	$63.6567	$63.66	$63.65	$63.70
Purchase #2	$38.25	9.172%	$41.7583	$41.76	$41.75	$41.80
Purchase #3	$7.40	4.593%	$7.7399	$7.74	$7.75	$7.70
Purchase #4	$168.91	3.733%	$175.2154	$175.22	$175.20	$175.20
Purchase #5	$157.78	7.714%	$169.9511	$169.95	$169.95	$170.00
Purchase #6	$83.67	8.632%	$90.8924	$90.89	$90.90	$90.90
Purchase #7	$89.79	10.376%	$99.1066	$99.11	$99.10	$99.10
7 purchase totals =	$604.57		$648.3204	$648.33	$648.30	$648.40