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	$204.26	11.362%	$227.468	$227.47	$227.45	$227.50
Purchase #2	$37.51	8.206%	$40.5881	$40.59	$40.60	$40.60
Purchase #3	$47.43	9.570%	$51.9691	$51.97	$51.95	$52.00
Purchase #4	$107.81	11.736%	$120.4626	$120.46	$120.45	$120.50
Purchase #5	$12.69	9.367%	$13.8787	$13.88	$13.90	$13.90
Purchase #6	$159.95	4.828%	$167.6724	$167.67	$167.65	$167.70
Purchase #7	$127.68	12.366%	$143.4689	$143.47	$143.45	$143.50
7 purchase totals =	$697.33		$765.5078	$765.51	$765.45	$765.70