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	$151.82	11.331%	$169.0227	$169.02	$169.00	$169.00
Purchase #2	$165.59	5.221%	$174.2355	$174.24	$174.25	$174.20
Purchase #3	$83.57	4.207%	$87.0858	$87.09	$87.10	$87.10
Purchase #4	$165.97	11.149%	$184.474	$184.47	$184.45	$184.50
Purchase #5	$131.25	6.222%	$139.4164	$139.42	$139.40	$139.40
Purchase #6	$68.30	13.604%	$77.5915	$77.59	$77.60	$77.60
Purchase #7	$61.46	7.496%	$66.067	$66.07	$66.05	$66.10
7 purchase totals =	$827.96		$897.8929	$897.90	$897.85	$897.90