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	$235.47	13.640%	$267.5881	$267.59	$267.60	$267.60
Purchase #2	$69.52	4.622%	$72.7332	$72.73	$72.75	$72.70
Purchase #3	$60.72	10.312%	$66.9814	$66.98	$67.00	$67.00
Purchase #4	$246.48	5.859%	$260.9213	$260.92	$260.90	$260.90
Purchase #5	$158.43	4.790%	$166.0188	$166.02	$166.00	$166.00
Purchase #6	$10.68	13.534%	$12.1254	$12.13	$12.15	$12.10
Purchase #7	$163.29	9.756%	$179.2206	$179.22	$179.20	$179.20
7 purchase totals =	$944.59		$1,025.5888	$1,025.59	$1,025.60	$1,025.50