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	$35.43	13.594%	$40.2464	$40.25	$40.25	$40.20
Purchase #2	$151.49	9.648%	$166.1058	$166.11	$166.10	$166.10
Purchase #3	$176.28	11.496%	$196.5451	$196.55	$196.55	$196.50
Purchase #4	$58.75	13.277%	$66.5502	$66.55	$66.55	$66.60
Purchase #5	$238.63	10.201%	$262.9726	$262.97	$262.95	$263.00
Purchase #6	$105.94	9.759%	$116.2787	$116.28	$116.30	$116.30
Purchase #7	$192.52	13.503%	$218.516	$218.52	$218.50	$218.50
7 purchase totals =	$959.04		$1,067.2148	$1,067.23	$1,067.20	$1,067.20