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	$87.99	13.269%	$99.6654	$99.67	$99.65	$99.70
Purchase #2	$215.83	11.812%	$241.3238	$241.32	$241.30	$241.30
Purchase #3	$66.49	3.193%	$68.613	$68.61	$68.60	$68.60
Purchase #4	$34.72	7.410%	$37.2928	$37.29	$37.30	$37.30
Purchase #5	$155.83	8.429%	$168.9649	$168.96	$168.95	$169.00
Purchase #6	$50.85	13.209%	$57.5668	$57.57	$57.55	$57.60
Purchase #7	$223.81	4.350%	$233.5457	$233.55	$233.55	$233.50
7 purchase totals =	$835.52		$906.9724	$906.97	$906.90	$907.00