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	$42.60	13.581%	$48.3855	$48.39	$48.40	$48.40
Purchase #2	$79.72	13.374%	$90.3818	$90.38	$90.40	$90.40
Purchase #3	$206.77	10.375%	$228.2224	$228.22	$228.20	$228.20
Purchase #4	$40.30	11.181%	$44.8059	$44.81	$44.80	$44.80
Purchase #5	$45.35	3.668%	$47.0134	$47.01	$47.00	$47.00
Purchase #6	$28.95	10.670%	$32.039	$32.04	$32.05	$32.00
Purchase #7	$220.83	6.764%	$235.7669	$235.77	$235.75	$235.80
7 purchase totals =	$664.52		$726.6149	$726.62	$726.60	$726.60