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	$83.69	5.870%	$88.6026	$88.60	$88.60	$88.60
Purchase #2	$93.69	7.325%	$100.5528	$100.55	$100.55	$100.60
Purchase #3	$54.77	12.863%	$61.8151	$61.82	$61.80	$61.80
Purchase #4	$134.39	3.868%	$139.5882	$139.59	$139.60	$139.60
Purchase #5	$235.61	3.859%	$244.7022	$244.70	$244.70	$244.70
Purchase #6	$25.58	13.455%	$29.0218	$29.02	$29.00	$29.00
Purchase #7	$54.33	6.610%	$57.9212	$57.92	$57.90	$57.90
7 purchase totals =	$682.06		$722.2039	$722.20	$722.15	$722.20