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	$226.55	9.406%	$247.8593	$247.86	$247.85	$247.90
Purchase #2	$61.62	12.454%	$69.2942	$69.29	$69.30	$69.30
Purchase #3	$37.78	6.567%	$40.261	$40.26	$40.25	$40.30
Purchase #4	$24.83	10.130%	$27.3453	$27.35	$27.35	$27.30
Purchase #5	$74.67	11.311%	$83.1159	$83.12	$83.10	$83.10
Purchase #6	$132.45	5.496%	$139.7295	$139.73	$139.75	$139.70
Purchase #7	$179.92	9.358%	$196.7569	$196.76	$196.75	$196.80
7 purchase totals =	$737.82		$804.3621	$804.37	$804.35	$804.40