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	$131.96	11.539%	$147.1869	$147.19	$147.20	$147.20
Purchase #2	$61.46	7.468%	$66.0498	$66.05	$66.05	$66.00
Purchase #3	$114.66	3.442%	$118.6066	$118.61	$118.60	$118.60
Purchase #4	$205.37	6.186%	$218.0742	$218.07	$218.05	$218.10
Purchase #5	$182.69	4.305%	$190.5548	$190.55	$190.55	$190.60
Purchase #6	$37.44	10.863%	$41.5071	$41.51	$41.50	$41.50
Purchase #7	$151.88	13.381%	$172.2031	$172.20	$172.20	$172.20
7 purchase totals =	$885.46		$954.1825	$954.18	$954.15	$954.20