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	$233.29	9.644%	$255.7885	$255.79	$255.80	$255.80
Purchase #2	$39.68	9.817%	$43.5754	$43.58	$43.60	$43.60
Purchase #3	$87.96	8.437%	$95.3812	$95.38	$95.40	$95.40
Purchase #4	$53.41	13.651%	$60.701	$60.70	$60.70	$60.70
Purchase #5	$192.89	12.175%	$216.3744	$216.37	$216.35	$216.40
Purchase #6	$117.54	4.803%	$123.1854	$123.19	$123.20	$123.20
Purchase #7	$76.78	7.769%	$82.745	$82.75	$82.75	$82.70
7 purchase totals =	$801.55		$877.7509	$877.76	$877.80	$877.80