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	$213.89	8.443%	$231.9487	$231.95	$231.95	$231.90
Purchase #2	$78.45	3.822%	$81.4484	$81.45	$81.45	$81.40
Purchase #3	$39.30	11.297%	$43.7397	$43.74	$43.75	$43.70
Purchase #4	$37.81	7.503%	$40.6469	$40.65	$40.65	$40.60
Purchase #5	$76.26	11.392%	$84.9475	$84.95	$84.95	$84.90
Purchase #6	$74.76	4.421%	$78.0651	$78.07	$78.05	$78.10
Purchase #7	$81.54	10.630%	$90.2077	$90.21	$90.20	$90.20
7 purchase totals =	$602.01		$651.0040	$651.02	$651.00	$650.80