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	$82.88	11.490%	$92.4029	$92.40	$92.40	$92.40
Purchase #2	$132.59	10.715%	$146.797	$146.80	$146.80	$146.80
Purchase #3	$241.87	13.511%	$274.5491	$274.55	$274.55	$274.50
Purchase #4	$71.50	5.635%	$75.529	$75.53	$75.55	$75.50
Purchase #5	$165.74	3.233%	$171.0984	$171.10	$171.10	$171.10
Purchase #6	$218.68	9.103%	$238.5864	$238.59	$238.60	$238.60
Purchase #7	$151.45	11.484%	$168.8425	$168.84	$168.85	$168.80
7 purchase totals =	$1,064.71		$1,167.8053	$1,167.81	$1,167.85	$1,167.70