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	$71.92	6.363%	$76.4963	$76.50	$76.50	$76.50
Purchase #2	$70.62	9.580%	$77.3854	$77.39	$77.40	$77.40
Purchase #3	$165.82	10.547%	$183.309	$183.31	$183.30	$183.30
Purchase #4	$139.77	9.102%	$152.4919	$152.49	$152.50	$152.50
Purchase #5	$102.44	8.583%	$111.2324	$111.23	$111.25	$111.20
Purchase #6	$35.56	12.553%	$40.0238	$40.02	$40.00	$40.00
Purchase #7	$224.60	13.558%	$255.0513	$255.05	$255.05	$255.10
7 purchase totals =	$810.73		$895.9901	$895.99	$896.00	$896.00