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	$112.36	5.725%	$118.7926	$118.79	$118.80	$118.80
Purchase #2	$153.58	4.493%	$160.4803	$160.48	$160.50	$160.50
Purchase #3	$17.55	13.574%	$19.9322	$19.93	$19.95	$19.90
Purchase #4	$228.77	11.627%	$255.3691	$255.37	$255.35	$255.40
Purchase #5	$131.74	6.202%	$139.9105	$139.91	$139.90	$139.90
Purchase #6	$95.89	13.833%	$109.1545	$109.15	$109.15	$109.20
Purchase #7	$141.27	6.304%	$150.1757	$150.18	$150.20	$150.20
7 purchase totals =	$881.16		$953.8149	$953.81	$953.85	$953.90