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	$168.68	9.206%	$184.2087	$184.21	$184.20	$184.20
Purchase #2	$204.81	5.340%	$215.7469	$215.75	$215.75	$215.70
Purchase #3	$133.59	11.230%	$148.5922	$148.59	$148.60	$148.60
Purchase #4	$147.58	13.561%	$167.5933	$167.59	$167.60	$167.60
Purchase #5	$31.37	6.500%	$33.4091	$33.41	$33.40	$33.40
Purchase #6	$10.84	4.785%	$11.3587	$11.36	$11.35	$11.40
Purchase #7	$155.44	10.333%	$171.5016	$171.50	$171.50	$171.50
7 purchase totals =	$852.31		$932.4105	$932.41	$932.40	$932.40