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	$66.86	4.477%	$69.8533	$69.85	$69.85	$69.90
Purchase #2	$210.27	3.627%	$217.8965	$217.90	$217.90	$217.90
Purchase #3	$29.49	6.236%	$31.329	$31.33	$31.35	$31.30
Purchase #4	$104.74	4.390%	$109.3381	$109.34	$109.35	$109.30
Purchase #5	$19.42	8.518%	$21.0742	$21.07	$21.05	$21.10
Purchase #6	$37.98	10.370%	$41.9185	$41.92	$41.90	$41.90
Purchase #7	$86.93	8.761%	$94.5459	$94.55	$94.55	$94.50
7 purchase totals =	$555.69		$585.9555	$585.96	$585.95	$585.90