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	$110.89	11.239%	$123.3529	$123.35	$123.35	$123.40
Purchase #2	$106.99	4.545%	$111.8527	$111.85	$111.85	$111.90
Purchase #3	$40.86	6.571%	$43.5449	$43.54	$43.55	$43.50
Purchase #4	$90.34	3.598%	$93.5904	$93.59	$93.60	$93.60
Purchase #5	$194.53	12.523%	$218.891	$218.89	$218.90	$218.90
Purchase #6	$78.36	6.470%	$83.4299	$83.43	$83.45	$83.40
Purchase #7	$77.90	7.169%	$83.4847	$83.48	$83.50	$83.50
7 purchase totals =	$699.87		$758.1465	$758.13	$758.20	$758.20