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	$214.36	3.384%	$221.6139	$221.61	$221.60	$221.60
Purchase #2	$173.93	6.745%	$185.6616	$185.66	$185.65	$185.70
Purchase #3	$33.44	13.334%	$37.8989	$37.90	$37.90	$37.90
Purchase #4	$106.42	11.183%	$118.3209	$118.32	$118.30	$118.30
Purchase #5	$226.31	13.316%	$256.4454	$256.45	$256.45	$256.40
Purchase #6	$66.39	13.347%	$75.2511	$75.25	$75.25	$75.30
Purchase #7	$51.25	4.709%	$53.6634	$53.66	$53.65	$53.70
7 purchase totals =	$872.10		$948.8552	$948.85	$948.80	$948.90