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	$10.48	8.390%	$11.3593	$11.36	$11.35	$11.40
Purchase #2	$75.25	11.374%	$83.8089	$83.81	$83.80	$83.80
Purchase #3	$38.47	13.649%	$43.7208	$43.72	$43.70	$43.70
Purchase #4	$245.86	11.195%	$273.384	$273.38	$273.40	$273.40
Purchase #5	$11.46	4.852%	$12.016	$12.02	$12.00	$12.00
Purchase #6	$169.87	10.634%	$187.934	$187.93	$187.95	$187.90
Purchase #7	$67.95	5.694%	$71.8191	$71.82	$71.80	$71.80
7 purchase totals =	$619.34		$684.0421	$684.04	$684.00	$684.00