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	$31.49	13.443%	$35.7232	$35.72	$35.70	$35.70
Purchase #2	$83.39	8.426%	$90.4164	$90.42	$90.40	$90.40
Purchase #3	$177.77	11.760%	$198.6758	$198.68	$198.70	$198.70
Purchase #4	$50.32	11.563%	$56.1385	$56.14	$56.15	$56.10
Purchase #5	$16.34	10.585%	$18.0696	$18.07	$18.05	$18.10
Purchase #6	$156.90	11.715%	$175.2808	$175.28	$175.30	$175.30
Purchase #7	$25.78	4.735%	$27.0007	$27.00	$27.00	$27.00
7 purchase totals =	$541.99		$601.3050	$601.31	$601.30	$601.30