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	$95.79	5.711%	$101.2606	$101.26	$101.25	$101.30
Purchase #2	$51.57	8.830%	$56.1236	$56.12	$56.10	$56.10
Purchase #3	$67.67	5.744%	$71.557	$71.56	$71.55	$71.60
Purchase #4	$76.59	13.645%	$87.0407	$87.04	$87.05	$87.00
Purchase #5	$227.44	7.679%	$244.9051	$244.91	$244.90	$244.90
Purchase #6	$107.53	3.639%	$111.443	$111.44	$111.45	$111.40
Purchase #7	$93.30	7.406%	$100.2098	$100.21	$100.20	$100.20
7 purchase totals =	$719.89		$772.5398	$772.54	$772.50	$772.50