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	$135.28	3.533%	$140.0594	$140.06	$140.05	$140.10
Purchase #2	$221.30	7.635%	$238.1963	$238.20	$238.20	$238.20
Purchase #3	$147.93	12.105%	$165.8369	$165.84	$165.85	$165.80
Purchase #4	$175.47	11.703%	$196.0053	$196.01	$196.00	$196.00
Purchase #5	$67.69	7.131%	$72.517	$72.52	$72.50	$72.50
Purchase #6	$137.67	5.442%	$145.162	$145.16	$145.15	$145.20
Purchase #7	$5.73	13.659%	$6.5127	$6.51	$6.50	$6.50
7 purchase totals =	$891.07		$964.2896	$964.30	$964.25	$964.30