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	$118.63	3.794%	$123.1308	$123.13	$123.15	$123.10
Purchase #2	$75.65	8.213%	$81.8631	$81.86	$81.85	$81.90
Purchase #3	$42.52	11.620%	$47.4608	$47.46	$47.45	$47.50
Purchase #4	$212.77	8.784%	$231.4597	$231.46	$231.45	$231.50
Purchase #5	$133.93	13.495%	$152.0039	$152.00	$152.00	$152.00
Purchase #6	$132.43	7.219%	$141.9901	$141.99	$142.00	$142.00
Purchase #7	$91.84	13.766%	$104.4827	$104.48	$104.50	$104.50
7 purchase totals =	$807.77		$882.3911	$882.38	$882.40	$882.50