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	$38.42	8.633%	$41.7368	$41.74	$41.75	$41.70
Purchase #2	$9.53	11.112%	$10.589	$10.59	$10.60	$10.60
Purchase #3	$13.45	7.303%	$14.4323	$14.43	$14.45	$14.40
Purchase #4	$225.30	8.839%	$245.2143	$245.21	$245.20	$245.20
Purchase #5	$29.58	10.849%	$32.7891	$32.79	$32.80	$32.80
Purchase #6	$132.38	6.140%	$140.5081	$140.51	$140.50	$140.50
Purchase #7	$34.76	8.143%	$37.5905	$37.59	$37.60	$37.60
7 purchase totals =	$483.42		$522.8601	$522.86	$522.90	$522.80