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	$212.85	6.761%	$227.2408	$227.24	$227.25	$227.20
Purchase #2	$119.35	3.166%	$123.1286	$123.13	$123.15	$123.10
Purchase #3	$130.45	12.484%	$146.7354	$146.74	$146.75	$146.70
Purchase #4	$38.66	10.216%	$42.6095	$42.61	$42.60	$42.60
Purchase #5	$209.68	13.719%	$238.446	$238.45	$238.45	$238.40
Purchase #6	$116.25	13.748%	$132.2321	$132.23	$132.25	$132.20
Purchase #7	$117.92	13.282%	$133.5821	$133.58	$133.60	$133.60
7 purchase totals =	$945.16		$1,043.9745	$1,043.98	$1,044.05	$1,043.80