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	$59.79	8.332%	$64.7717	$64.77	$64.75	$64.80
Purchase #2	$146.84	5.760%	$155.298	$155.30	$155.30	$155.30
Purchase #3	$29.93	12.254%	$33.5976	$33.60	$33.60	$33.60
Purchase #4	$133.70	12.631%	$150.5876	$150.59	$150.60	$150.60
Purchase #5	$247.90	3.105%	$255.5973	$255.60	$255.60	$255.60
Purchase #6	$9.56	12.201%	$10.7264	$10.73	$10.75	$10.70
Purchase #7	$222.47	11.434%	$247.9072	$247.91	$247.90	$247.90
7 purchase totals =	$850.19		$918.4858	$918.50	$918.50	$918.50