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	$17.32	3.718%	$17.964	$17.96	$17.95	$18.00
Purchase #2	$70.75	10.348%	$78.0712	$78.07	$78.05	$78.10
Purchase #3	$215.55	10.189%	$237.5124	$237.51	$237.50	$237.50
Purchase #4	$104.45	13.420%	$118.4672	$118.47	$118.45	$118.50
Purchase #5	$197.42	3.277%	$203.8895	$203.89	$203.90	$203.90
Purchase #6	$137.25	6.547%	$146.2358	$146.24	$146.25	$146.20
Purchase #7	$54.81	8.507%	$59.4727	$59.47	$59.45	$59.50
7 purchase totals =	$797.55		$861.6128	$861.61	$861.55	$861.70