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	$82.34	12.321%	$92.4851	$92.49	$92.50	$92.50
Purchase #2	$90.38	5.184%	$95.0653	$95.07	$95.05	$95.10
Purchase #3	$197.87	12.544%	$222.6908	$222.69	$222.70	$222.70
Purchase #4	$135.75	12.363%	$152.5328	$152.53	$152.55	$152.50
Purchase #5	$95.78	12.231%	$107.4949	$107.49	$107.50	$107.50
Purchase #6	$74.32	6.118%	$78.8669	$78.87	$78.85	$78.90
Purchase #7	$133.55	7.595%	$143.6931	$143.69	$143.70	$143.70
7 purchase totals =	$809.99		$892.8289	$892.83	$892.85	$892.90