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	$50.93	12.575%	$57.3344	$57.33	$57.35	$57.30
Purchase #2	$73.85	12.589%	$83.147	$83.15	$83.15	$83.10
Purchase #3	$195.85	7.175%	$209.9022	$209.90	$209.90	$209.90
Purchase #4	$104.29	13.151%	$118.0052	$118.01	$118.00	$118.00
Purchase #5	$11.81	4.504%	$12.3419	$12.34	$12.35	$12.30
Purchase #6	$213.55	12.165%	$239.5284	$239.53	$239.55	$239.50
Purchase #7	$215.89	4.243%	$225.0502	$225.05	$225.05	$225.10
7 purchase totals =	$866.17		$945.3093	$945.31	$945.35	$945.20