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	$106.54	3.106%	$109.8491	$109.85	$109.85	$109.80
Purchase #2	$132.67	13.317%	$150.3377	$150.34	$150.35	$150.30
Purchase #3	$61.49	4.660%	$64.3554	$64.36	$64.35	$64.40
Purchase #4	$39.63	3.176%	$40.8886	$40.89	$40.90	$40.90
Purchase #5	$94.52	13.546%	$107.3237	$107.32	$107.30	$107.30
Purchase #6	$51.89	5.342%	$54.662	$54.66	$54.65	$54.70
Purchase #7	$176.32	7.860%	$190.1788	$190.18	$190.20	$190.20
7 purchase totals =	$663.06		$717.5953	$717.60	$717.60	$717.60