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	$147.60	12.576%	$166.1622	$166.16	$166.15	$166.20
Purchase #2	$127.65	3.796%	$132.4956	$132.50	$132.50	$132.50
Purchase #3	$153.44	10.461%	$169.4914	$169.49	$169.50	$169.50
Purchase #4	$125.80	4.540%	$131.5113	$131.51	$131.50	$131.50
Purchase #5	$94.35	8.340%	$102.2188	$102.22	$102.20	$102.20
Purchase #6	$222.55	12.599%	$250.5891	$250.59	$250.60	$250.60
Purchase #7	$93.31	9.325%	$102.0112	$102.01	$102.00	$102.00
7 purchase totals =	$964.70		$1,054.4796	$1,054.48	$1,054.45	$1,054.50