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	$40.96	10.160%	$45.1215	$45.12	$45.10	$45.10
Purchase #2	$9.67	4.792%	$10.1334	$10.13	$10.15	$10.10
Purchase #3	$57.90	13.570%	$65.757	$65.76	$65.75	$65.80
Purchase #4	$9.48	8.699%	$10.3047	$10.30	$10.30	$10.30
Purchase #5	$18.90	6.741%	$20.174	$20.17	$20.15	$20.20
Purchase #6	$67.38	8.572%	$73.1558	$73.16	$73.15	$73.20
Purchase #7	$134.37	6.593%	$143.229	$143.23	$143.25	$143.20
7 purchase totals =	$338.66		$367.8754	$367.87	$367.85	$367.90