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	$209.94	4.596%	$219.5888	$219.59	$219.60	$219.60
Purchase #2	$68.79	4.141%	$71.6386	$71.64	$71.65	$71.60
Purchase #3	$108.85	7.682%	$117.2119	$117.21	$117.20	$117.20
Purchase #4	$137.91	10.779%	$152.7753	$152.78	$152.80	$152.80
Purchase #5	$14.25	4.168%	$14.8439	$14.84	$14.85	$14.80
Purchase #6	$75.29	4.484%	$78.666	$78.67	$78.65	$78.70
Purchase #7	$177.89	10.657%	$196.8477	$196.85	$196.85	$196.80
7 purchase totals =	$792.92		$851.5722	$851.58	$851.60	$851.50