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	$200.45	8.819%	$218.1277	$218.13	$218.15	$218.10
Purchase #2	$53.52	11.387%	$59.6143	$59.61	$59.60	$59.60
Purchase #3	$128.79	10.593%	$142.4327	$142.43	$142.45	$142.40
Purchase #4	$82.82	6.762%	$88.4203	$88.42	$88.40	$88.40
Purchase #5	$246.56	10.698%	$272.937	$272.94	$272.95	$272.90
Purchase #6	$121.64	4.863%	$127.5554	$127.56	$127.55	$127.60
Purchase #7	$28.88	8.752%	$31.4076	$31.41	$31.40	$31.40
7 purchase totals =	$862.66		$940.4950	$940.50	$940.50	$940.40