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	$83.50	13.815%	$95.0355	$95.04	$95.05	$95.00
Purchase #2	$172.77	8.533%	$187.5125	$187.51	$187.50	$187.50
Purchase #3	$93.78	7.594%	$100.9017	$100.90	$100.90	$100.90
Purchase #4	$143.28	11.351%	$159.5437	$159.54	$159.55	$159.50
Purchase #5	$178.45	4.166%	$185.8842	$185.88	$185.90	$185.90
Purchase #6	$28.53	13.392%	$32.3507	$32.35	$32.35	$32.40
Purchase #7	$164.49	11.411%	$183.26	$183.26	$183.25	$183.30
7 purchase totals =	$864.80		$944.4883	$944.48	$944.50	$944.50