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	$12.77	4.463%	$13.3399	$13.34	$13.35	$13.30
Purchase #2	$168.95	3.720%	$175.2349	$175.23	$175.25	$175.20
Purchase #3	$164.48	5.160%	$172.9672	$172.97	$172.95	$173.00
Purchase #4	$160.61	7.815%	$173.1617	$173.16	$173.15	$173.20
Purchase #5	$128.83	9.519%	$141.0933	$141.09	$141.10	$141.10
Purchase #6	$146.43	3.810%	$152.009	$152.01	$152.00	$152.00
Purchase #7	$206.76	13.799%	$235.2908	$235.29	$235.30	$235.30
7 purchase totals =	$988.83		$1,063.0968	$1,063.09	$1,063.10	$1,063.10