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	$132.56	9.622%	$145.3149	$145.31	$145.30	$145.30
Purchase #2	$132.60	7.854%	$143.0144	$143.01	$143.00	$143.00
Purchase #3	$190.61	13.708%	$216.7388	$216.74	$216.75	$216.70
Purchase #4	$56.58	4.142%	$58.9235	$58.92	$58.90	$58.90
Purchase #5	$226.96	6.579%	$241.8917	$241.89	$241.90	$241.90
Purchase #6	$99.85	4.450%	$104.2933	$104.29	$104.30	$104.30
Purchase #7	$69.87	3.738%	$72.4817	$72.48	$72.50	$72.50
7 purchase totals =	$909.03		$982.6583	$982.64	$982.65	$982.60