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	$73.93	11.587%	$82.4963	$82.50	$82.50	$82.50
Purchase #2	$81.51	13.372%	$92.4095	$92.41	$92.40	$92.40
Purchase #3	$83.44	4.105%	$86.8652	$86.87	$86.85	$86.90
Purchase #4	$34.42	10.126%	$37.9054	$37.91	$37.90	$37.90
Purchase #5	$147.36	7.632%	$158.6065	$158.61	$158.60	$158.60
Purchase #6	$26.29	13.591%	$29.8631	$29.86	$29.85	$29.90
Purchase #7	$144.43	13.599%	$164.071	$164.07	$164.05	$164.10
7 purchase totals =	$591.38		$652.2170	$652.23	$652.15	$652.30