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	$63.88	12.290%	$71.7309	$71.73	$71.75	$71.70
Purchase #2	$195.46	10.513%	$216.0087	$216.01	$216.00	$216.00
Purchase #3	$114.47	10.484%	$126.471	$126.47	$126.45	$126.50
Purchase #4	$90.47	5.328%	$95.2902	$95.29	$95.30	$95.30
Purchase #5	$248.46	9.590%	$272.2873	$272.29	$272.30	$272.30
Purchase #6	$247.56	10.418%	$273.3508	$273.35	$273.35	$273.40
Purchase #7	$10.26	10.645%	$11.3522	$11.35	$11.35	$11.40
7 purchase totals =	$970.56		$1,066.4911	$1,066.49	$1,066.50	$1,066.60