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	$162.62	6.267%	$172.8114	$172.81	$172.80	$172.80
Purchase #2	$30.50	13.401%	$34.5873	$34.59	$34.60	$34.60
Purchase #3	$135.34	8.451%	$146.7776	$146.78	$146.80	$146.80
Purchase #4	$73.28	7.547%	$78.8104	$78.81	$78.80	$78.80
Purchase #5	$28.89	3.233%	$29.824	$29.82	$29.80	$29.80
Purchase #6	$209.83	9.741%	$230.2695	$230.27	$230.25	$230.30
Purchase #7	$64.70	3.828%	$67.1767	$67.18	$67.20	$67.20
7 purchase totals =	$705.16		$760.2569	$760.26	$760.25	$760.30