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	$87.66	9.211%	$95.7344	$95.73	$95.75	$95.70
Purchase #2	$167.36	10.660%	$185.2006	$185.20	$185.20	$185.20
Purchase #3	$193.37	12.212%	$216.9843	$216.98	$217.00	$217.00
Purchase #4	$122.56	11.418%	$136.5539	$136.55	$136.55	$136.60
Purchase #5	$154.37	9.131%	$168.4655	$168.47	$168.45	$168.50
Purchase #6	$29.37	11.382%	$32.7129	$32.71	$32.70	$32.70
Purchase #7	$83.72	8.503%	$90.8387	$90.84	$90.85	$90.80
7 purchase totals =	$838.41		$926.4903	$926.48	$926.50	$926.50