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	$41.60	7.258%	$44.6193	$44.62	$44.60	$44.60
Purchase #2	$225.55	8.218%	$244.0857	$244.09	$244.10	$244.10
Purchase #3	$20.99	3.783%	$21.7841	$21.78	$21.80	$21.80
Purchase #4	$65.31	8.706%	$70.9959	$71.00	$71.00	$71.00
Purchase #5	$41.47	10.555%	$45.8472	$45.85	$45.85	$45.80
Purchase #6	$72.57	13.701%	$82.5128	$82.51	$82.50	$82.50
Purchase #7	$48.42	12.817%	$54.626	$54.63	$54.65	$54.60
7 purchase totals =	$515.91		$564.4710	$564.48	$564.50	$564.40