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	$96.47	8.476%	$104.6468	$104.65	$104.65	$104.60
Purchase #2	$7.44	5.558%	$7.8535	$7.85	$7.85	$7.90
Purchase #3	$138.90	9.205%	$151.6857	$151.69	$151.70	$151.70
Purchase #4	$105.89	3.828%	$109.9435	$109.94	$109.95	$109.90
Purchase #5	$79.68	7.332%	$85.5221	$85.52	$85.50	$85.50
Purchase #6	$116.94	13.130%	$132.2942	$132.29	$132.30	$132.30
Purchase #7	$49.45	8.655%	$53.7299	$53.73	$53.75	$53.70
7 purchase totals =	$594.77		$645.6757	$645.67	$645.70	$645.60