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	$247.94	7.555%	$266.6719	$266.67	$266.65	$266.70
Purchase #2	$191.29	10.795%	$211.9398	$211.94	$211.95	$211.90
Purchase #3	$82.42	7.572%	$88.6608	$88.66	$88.65	$88.70
Purchase #4	$59.74	5.152%	$62.8178	$62.82	$62.80	$62.80
Purchase #5	$147.89	13.854%	$168.3787	$168.38	$168.40	$168.40
Purchase #6	$205.76	8.347%	$222.9348	$222.93	$222.95	$222.90
Purchase #7	$137.65	3.725%	$142.7775	$142.78	$142.80	$142.80
7 purchase totals =	$1,072.69		$1,164.1813	$1,164.18	$1,164.20	$1,164.20