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	$148.82	12.796%	$167.863	$167.86	$167.85	$167.90
Purchase #2	$182.28	10.169%	$200.8161	$200.82	$200.80	$200.80
Purchase #3	$112.61	3.161%	$116.1696	$116.17	$116.15	$116.20
Purchase #4	$199.51	4.813%	$209.1124	$209.11	$209.10	$209.10
Purchase #5	$60.94	9.651%	$66.8213	$66.82	$66.80	$66.80
Purchase #6	$16.31	11.640%	$18.2085	$18.21	$18.20	$18.20
Purchase #7	$106.45	5.796%	$112.6198	$112.62	$112.60	$112.60
7 purchase totals =	$826.92		$891.6107	$891.61	$891.50	$891.60