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	$201.30	7.473%	$216.3431	$216.34	$216.35	$216.30
Purchase #2	$94.94	5.361%	$100.0297	$100.03	$100.05	$100.00
Purchase #3	$104.72	6.743%	$111.7813	$111.78	$111.80	$111.80
Purchase #4	$27.38	4.484%	$28.6077	$28.61	$28.60	$28.60
Purchase #5	$126.41	13.674%	$143.6953	$143.70	$143.70	$143.70
Purchase #6	$249.26	6.756%	$266.1	$266.10	$266.10	$266.10
Purchase #7	$85.34	6.184%	$90.6174	$90.62	$90.60	$90.60
7 purchase totals =	$889.35		$957.1745	$957.18	$957.20	$957.10