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	$171.28	7.337%	$183.8468	$183.85	$183.85	$183.80
Purchase #2	$68.45	6.534%	$72.9225	$72.92	$72.90	$72.90
Purchase #3	$66.28	3.788%	$68.7907	$68.79	$68.80	$68.80
Purchase #4	$123.51	7.858%	$133.2154	$133.22	$133.20	$133.20
Purchase #5	$132.35	7.119%	$141.772	$141.77	$141.75	$141.80
Purchase #6	$17.64	4.661%	$18.4622	$18.46	$18.45	$18.50
Purchase #7	$182.46	4.394%	$190.4773	$190.48	$190.50	$190.50
7 purchase totals =	$761.97		$809.4869	$809.49	$809.45	$809.50