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	$39.58	4.407%	$41.3243	$41.32	$41.30	$41.30
Purchase #2	$10.62	9.345%	$11.6124	$11.61	$11.60	$11.60
Purchase #3	$139.41	8.773%	$151.6404	$151.64	$151.65	$151.60
Purchase #4	$168.70	10.171%	$185.8585	$185.86	$185.85	$185.90
Purchase #5	$109.43	8.544%	$118.7797	$118.78	$118.80	$118.80
Purchase #6	$15.96	11.817%	$17.846	$17.85	$17.85	$17.80
Purchase #7	$174.46	5.663%	$184.3397	$184.34	$184.35	$184.30
7 purchase totals =	$658.16		$711.4010	$711.40	$711.40	$711.30