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	$23.49	4.139%	$24.4623	$24.46	$24.45	$24.50
Purchase #2	$177.74	7.379%	$190.8554	$190.86	$190.85	$190.90
Purchase #3	$52.36	4.266%	$54.5937	$54.59	$54.60	$54.60
Purchase #4	$232.37	10.407%	$256.5527	$256.55	$256.55	$256.60
Purchase #5	$62.37	8.432%	$67.629	$67.63	$67.65	$67.60
Purchase #6	$132.92	5.242%	$139.8877	$139.89	$139.90	$139.90
Purchase #7	$202.36	9.244%	$221.0662	$221.07	$221.05	$221.10
7 purchase totals =	$883.61		$955.0470	$955.05	$955.05	$955.20