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	$223.79	10.175%	$246.5606	$246.56	$246.55	$246.60
Purchase #2	$19.86	4.622%	$20.7779	$20.78	$20.80	$20.80
Purchase #3	$118.47	4.768%	$124.1186	$124.12	$124.10	$124.10
Purchase #4	$209.51	11.470%	$233.5408	$233.54	$233.55	$233.50
Purchase #5	$52.87	12.487%	$59.4719	$59.47	$59.45	$59.50
Purchase #6	$67.82	13.353%	$76.876	$76.88	$76.90	$76.90
Purchase #7	$35.36	10.630%	$39.1188	$39.12	$39.10	$39.10
7 purchase totals =	$727.68		$800.4646	$800.47	$800.45	$800.50