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	$94.55	7.159%	$101.3188	$101.32	$101.30	$101.30
Purchase #2	$147.78	11.756%	$165.153	$165.15	$165.15	$165.20
Purchase #3	$50.57	7.631%	$54.429	$54.43	$54.45	$54.40
Purchase #4	$185.78	10.352%	$205.0119	$205.01	$205.00	$205.00
Purchase #5	$148.40	3.298%	$153.2942	$153.29	$153.30	$153.30
Purchase #6	$173.34	10.647%	$191.7955	$191.80	$191.80	$191.80
Purchase #7	$74.62	11.243%	$83.0095	$83.01	$83.00	$83.00
7 purchase totals =	$875.04		$954.0119	$954.01	$954.00	$954.00