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	$151.52	9.847%	$166.4402	$166.44	$166.45	$166.40
Purchase #2	$96.47	3.212%	$99.5686	$99.57	$99.55	$99.60
Purchase #3	$238.55	10.500%	$263.5978	$263.60	$263.60	$263.60
Purchase #4	$167.54	13.537%	$190.2199	$190.22	$190.20	$190.20
Purchase #5	$208.85	7.742%	$225.0192	$225.02	$225.00	$225.00
Purchase #6	$190.34	8.103%	$205.7633	$205.76	$205.75	$205.80
Purchase #7	$149.79	10.459%	$165.4565	$165.46	$165.45	$165.50
7 purchase totals =	$1,203.06		$1,316.0655	$1,316.07	$1,316.00	$1,316.10