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	$214.41	6.171%	$227.6412	$227.64	$227.65	$227.60
Purchase #2	$37.50	6.554%	$39.9578	$39.96	$39.95	$40.00
Purchase #3	$133.81	8.766%	$145.5398	$145.54	$145.55	$145.50
Purchase #4	$196.30	11.724%	$219.3142	$219.31	$219.30	$219.30
Purchase #5	$206.51	8.634%	$224.3401	$224.34	$224.35	$224.30
Purchase #6	$242.28	13.729%	$275.5426	$275.54	$275.55	$275.50
Purchase #7	$14.83	3.134%	$15.2948	$15.29	$15.30	$15.30
7 purchase totals =	$1,045.64		$1,147.6305	$1,147.62	$1,147.65	$1,147.50