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	$44.39	3.467%	$45.929	$45.93	$45.95	$45.90
Purchase #2	$102.80	13.484%	$116.6616	$116.66	$116.65	$116.70
Purchase #3	$70.58	3.137%	$72.7941	$72.79	$72.80	$72.80
Purchase #4	$123.96	4.227%	$129.1998	$129.20	$129.20	$129.20
Purchase #5	$25.33	8.630%	$27.516	$27.52	$27.50	$27.50
Purchase #6	$134.52	6.167%	$142.8158	$142.82	$142.80	$142.80
Purchase #7	$22.34	9.337%	$24.4259	$24.43	$24.45	$24.40
7 purchase totals =	$523.92		$559.3422	$559.35	$559.35	$559.30