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	$65.46	12.824%	$73.8546	$73.85	$73.85	$73.90
Purchase #2	$70.74	11.498%	$78.8737	$78.87	$78.85	$78.90
Purchase #3	$88.73	13.130%	$100.3802	$100.38	$100.40	$100.40
Purchase #4	$77.90	6.749%	$83.1575	$83.16	$83.15	$83.20
Purchase #5	$102.62	3.557%	$106.2702	$106.27	$106.25	$106.30
Purchase #6	$25.49	12.222%	$28.6054	$28.61	$28.60	$28.60
Purchase #7	$231.30	7.217%	$247.9929	$247.99	$248.00	$248.00
7 purchase totals =	$662.24		$719.1345	$719.13	$719.10	$719.30