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	$216.65	11.254%	$241.0318	$241.03	$241.05	$241.00
Purchase #2	$224.39	5.526%	$236.7898	$236.79	$236.80	$236.80
Purchase #3	$13.78	5.505%	$14.5386	$14.54	$14.55	$14.50
Purchase #4	$79.45	13.668%	$90.3092	$90.31	$90.30	$90.30
Purchase #5	$205.39	9.480%	$224.861	$224.86	$224.85	$224.90
Purchase #6	$90.45	5.759%	$95.659	$95.66	$95.65	$95.70
Purchase #7	$82.43	8.731%	$89.627	$89.63	$89.65	$89.60
7 purchase totals =	$912.54		$992.8164	$992.82	$992.85	$992.80