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	$98.94	10.343%	$109.1734	$109.17	$109.15	$109.20
Purchase #2	$239.61	7.126%	$256.6846	$256.68	$256.70	$256.70
Purchase #3	$8.96	11.669%	$10.0055	$10.01	$10.00	$10.00
Purchase #4	$92.85	8.700%	$100.928	$100.93	$100.95	$100.90
Purchase #5	$152.50	9.558%	$167.076	$167.08	$167.10	$167.10
Purchase #6	$41.68	3.740%	$43.2388	$43.24	$43.25	$43.20
Purchase #7	$130.37	12.325%	$146.4381	$146.44	$146.45	$146.40
7 purchase totals =	$764.91		$833.5444	$833.55	$833.60	$833.50