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	$213.58	4.328%	$222.8237	$222.82	$222.80	$222.80
Purchase #2	$59.31	11.774%	$66.2932	$66.29	$66.30	$66.30
Purchase #3	$216.65	5.130%	$227.7641	$227.76	$227.75	$227.80
Purchase #4	$17.71	10.756%	$19.6149	$19.61	$19.60	$19.60
Purchase #5	$20.31	5.523%	$21.4317	$21.43	$21.45	$21.40
Purchase #6	$125.29	13.451%	$142.1428	$142.14	$142.15	$142.10
Purchase #7	$55.33	9.842%	$60.7756	$60.78	$60.80	$60.80
7 purchase totals =	$708.18		$760.8460	$760.83	$760.85	$760.80