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	$83.73	4.521%	$87.5154	$87.52	$87.50	$87.50
Purchase #2	$32.44	4.273%	$33.8262	$33.83	$33.85	$33.80
Purchase #3	$76.47	6.690%	$81.5858	$81.59	$81.60	$81.60
Purchase #4	$210.77	8.493%	$228.6707	$228.67	$228.65	$228.70
Purchase #5	$22.83	9.145%	$24.9178	$24.92	$24.90	$24.90
Purchase #6	$122.73	7.115%	$131.4622	$131.46	$131.45	$131.50
Purchase #7	$57.74	6.651%	$61.5803	$61.58	$61.60	$61.60
7 purchase totals =	$606.71		$649.5584	$649.57	$649.55	$649.60