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	$68.53	6.300%	$72.8474	$72.85	$72.85	$72.80
Purchase #2	$27.67	11.632%	$30.8886	$30.89	$30.90	$30.90
Purchase #3	$43.90	7.610%	$47.2408	$47.24	$47.25	$47.20
Purchase #4	$131.37	4.214%	$136.9059	$136.91	$136.90	$136.90
Purchase #5	$205.65	4.795%	$215.5109	$215.51	$215.50	$215.50
Purchase #6	$66.75	11.760%	$74.5998	$74.60	$74.60	$74.60
Purchase #7	$208.49	4.270%	$217.3925	$217.39	$217.40	$217.40
7 purchase totals =	$752.36		$795.3859	$795.39	$795.40	$795.30