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	$119.80	3.454%	$123.9379	$123.94	$123.95	$123.90
Purchase #2	$130.44	6.833%	$139.353	$139.35	$139.35	$139.40
Purchase #3	$152.52	12.874%	$172.1554	$172.16	$172.15	$172.20
Purchase #4	$234.49	5.111%	$246.4748	$246.47	$246.45	$246.50
Purchase #5	$108.97	9.284%	$119.0868	$119.09	$119.10	$119.10
Purchase #6	$14.52	13.488%	$16.4785	$16.48	$16.50	$16.50
Purchase #7	$244.66	3.674%	$253.6488	$253.65	$253.65	$253.60
7 purchase totals =	$1,005.40		$1,071.1352	$1,071.14	$1,071.15	$1,071.20