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	$196.48	5.134%	$206.5673	$206.57	$206.55	$206.60
Purchase #2	$21.55	12.282%	$24.1968	$24.20	$24.20	$24.20
Purchase #3	$117.70	7.505%	$126.5334	$126.53	$126.55	$126.50
Purchase #4	$71.93	8.667%	$78.1642	$78.16	$78.15	$78.20
Purchase #5	$52.80	12.131%	$59.2052	$59.21	$59.20	$59.20
Purchase #6	$88.48	4.589%	$92.5403	$92.54	$92.55	$92.50
Purchase #7	$35.82	13.482%	$40.6493	$40.65	$40.65	$40.60
7 purchase totals =	$584.76		$627.8565	$627.86	$627.85	$627.80