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	$35.53	6.770%	$37.9354	$37.94	$37.95	$37.90
Purchase #2	$119.61	11.136%	$132.9298	$132.93	$132.95	$132.90
Purchase #3	$45.34	3.680%	$47.0085	$47.01	$47.00	$47.00
Purchase #4	$137.74	5.618%	$145.4782	$145.48	$145.50	$145.50
Purchase #5	$43.42	9.432%	$47.5154	$47.52	$47.50	$47.50
Purchase #6	$92.35	7.309%	$99.0999	$99.10	$99.10	$99.10
Purchase #7	$13.82	6.318%	$14.6931	$14.69	$14.70	$14.70
7 purchase totals =	$487.81		$524.6603	$524.67	$524.70	$524.60