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	$132.42	7.115%	$141.8417	$141.84	$141.85	$141.80
Purchase #2	$224.87	13.742%	$255.7716	$255.77	$255.75	$255.80
Purchase #3	$16.95	9.188%	$18.5074	$18.51	$18.50	$18.50
Purchase #4	$19.37	5.711%	$20.4762	$20.48	$20.50	$20.50
Purchase #5	$211.33	8.569%	$229.4389	$229.44	$229.45	$229.40
Purchase #6	$231.51	11.454%	$258.0272	$258.03	$258.05	$258.00
Purchase #7	$130.94	9.598%	$143.5076	$143.51	$143.50	$143.50
7 purchase totals =	$967.39		$1,067.5706	$1,067.58	$1,067.60	$1,067.50