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	$222.78	5.422%	$234.8591	$234.86	$234.85	$234.90
Purchase #2	$18.59	12.102%	$20.8398	$20.84	$20.85	$20.80
Purchase #3	$161.67	4.678%	$169.2329	$169.23	$169.25	$169.20
Purchase #4	$197.56	4.407%	$206.2665	$206.27	$206.25	$206.30
Purchase #5	$31.90	7.599%	$34.3241	$34.32	$34.30	$34.30
Purchase #6	$48.54	7.541%	$52.2004	$52.20	$52.20	$52.20
Purchase #7	$60.30	10.339%	$66.5344	$66.53	$66.55	$66.50
7 purchase totals =	$741.34		$784.2572	$784.25	$784.25	$784.20