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	$103.95	6.573%	$110.7826	$110.78	$110.80	$110.80
Purchase #2	$125.42	9.654%	$137.528	$137.53	$137.55	$137.50
Purchase #3	$95.35	10.383%	$105.2502	$105.25	$105.25	$105.30
Purchase #4	$247.69	10.864%	$274.599	$274.60	$274.60	$274.60
Purchase #5	$238.59	3.171%	$246.1557	$246.16	$246.15	$246.20
Purchase #6	$105.54	7.667%	$113.6318	$113.63	$113.65	$113.60
Purchase #7	$122.85	13.500%	$139.4348	$139.43	$139.45	$139.40
7 purchase totals =	$1,039.39		$1,127.3821	$1,127.38	$1,127.45	$1,127.40