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	$229.49	3.723%	$238.0339	$238.03	$238.05	$238.00
Purchase #2	$60.70	12.846%	$68.4975	$68.50	$68.50	$68.50
Purchase #3	$38.51	12.277%	$43.2379	$43.24	$43.25	$43.20
Purchase #4	$230.74	11.312%	$256.8413	$256.84	$256.85	$256.80
Purchase #5	$79.42	4.594%	$83.0686	$83.07	$83.05	$83.10
Purchase #6	$136.31	4.491%	$142.4317	$142.43	$142.45	$142.40
Purchase #7	$143.46	5.472%	$151.3101	$151.31	$151.30	$151.30
7 purchase totals =	$918.63		$983.4210	$983.42	$983.45	$983.30