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	$126.38	13.393%	$143.3061	$143.31	$143.30	$143.30
Purchase #2	$247.75	3.443%	$256.28	$256.28	$256.30	$256.30
Purchase #3	$78.93	5.204%	$83.0375	$83.04	$83.05	$83.00
Purchase #4	$219.35	7.328%	$235.424	$235.42	$235.40	$235.40
Purchase #5	$222.82	6.576%	$237.4726	$237.47	$237.45	$237.50
Purchase #6	$35.65	6.304%	$37.8974	$37.90	$37.90	$37.90
Purchase #7	$113.45	3.434%	$117.3459	$117.35	$117.35	$117.30
7 purchase totals =	$1,044.33		$1,110.7635	$1,110.77	$1,110.75	$1,110.70