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	$167.72	7.484%	$180.2722	$180.27	$180.25	$180.30
Purchase #2	$6.27	5.168%	$6.594	$6.59	$6.60	$6.60
Purchase #3	$97.73	4.268%	$101.9011	$101.90	$101.90	$101.90
Purchase #4	$37.67	8.517%	$40.8784	$40.88	$40.90	$40.90
Purchase #5	$121.89	4.824%	$127.77	$127.77	$127.75	$127.80
Purchase #6	$56.80	7.449%	$61.031	$61.03	$61.05	$61.00
Purchase #7	$24.50	9.672%	$26.8696	$26.87	$26.85	$26.90
7 purchase totals =	$512.58		$545.3163	$545.31	$545.30	$545.40