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	$242.86	6.460%	$258.5488	$258.55	$258.55	$258.50
Purchase #2	$12.98	7.299%	$13.9274	$13.93	$13.95	$13.90
Purchase #3	$131.34	10.431%	$145.0401	$145.04	$145.05	$145.00
Purchase #4	$241.63	8.636%	$262.4972	$262.50	$262.50	$262.50
Purchase #5	$101.56	9.700%	$111.4113	$111.41	$111.40	$111.40
Purchase #6	$5.88	9.214%	$6.4218	$6.42	$6.40	$6.40
Purchase #7	$60.48	11.410%	$67.3808	$67.38	$67.40	$67.40
7 purchase totals =	$796.73		$865.2274	$865.23	$865.25	$865.10