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	$135.32	9.810%	$148.5949	$148.59	$148.60	$148.60
Purchase #2	$80.61	5.646%	$85.1612	$85.16	$85.15	$85.20
Purchase #3	$101.26	9.435%	$110.8139	$110.81	$110.80	$110.80
Purchase #4	$98.89	6.714%	$105.5295	$105.53	$105.55	$105.50
Purchase #5	$185.37	6.191%	$196.8463	$196.85	$196.85	$196.80
Purchase #6	$15.52	11.286%	$17.2716	$17.27	$17.25	$17.30
Purchase #7	$134.94	10.644%	$149.303	$149.30	$149.30	$149.30
7 purchase totals =	$751.91		$813.5204	$813.51	$813.50	$813.50