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	$148.99	13.762%	$169.494	$169.49	$169.50	$169.50
Purchase #2	$192.34	13.450%	$218.2097	$218.21	$218.20	$218.20
Purchase #3	$69.85	5.861%	$73.9439	$73.94	$73.95	$73.90
Purchase #4	$55.72	6.706%	$59.4566	$59.46	$59.45	$59.50
Purchase #5	$132.75	5.417%	$139.9411	$139.94	$139.95	$139.90
Purchase #6	$11.39	4.528%	$11.9057	$11.91	$11.90	$11.90
Purchase #7	$148.44	7.502%	$159.576	$159.58	$159.60	$159.60
7 purchase totals =	$759.48		$832.5270	$832.53	$832.55	$832.50