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	$140.29	7.354%	$150.6069	$150.61	$150.60	$150.60
Purchase #2	$55.67	9.440%	$60.9252	$60.93	$60.95	$60.90
Purchase #3	$115.98	10.559%	$128.2263	$128.23	$128.25	$128.20
Purchase #4	$42.35	13.622%	$48.1189	$48.12	$48.10	$48.10
Purchase #5	$34.38	9.507%	$37.6485	$37.65	$37.65	$37.60
Purchase #6	$34.39	10.364%	$37.9542	$37.95	$37.95	$38.00
Purchase #7	$197.60	5.571%	$208.6083	$208.61	$208.60	$208.60
7 purchase totals =	$620.66		$672.0883	$672.10	$672.10	$672.00