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	$200.72	7.369%	$215.5111	$215.51	$215.50	$215.50
Purchase #2	$241.98	7.789%	$260.8278	$260.83	$260.85	$260.80
Purchase #3	$64.31	12.353%	$72.2542	$72.25	$72.25	$72.30
Purchase #4	$88.81	4.527%	$92.8304	$92.83	$92.85	$92.80
Purchase #5	$152.89	11.820%	$170.9616	$170.96	$170.95	$171.00
Purchase #6	$170.36	9.669%	$186.8321	$186.83	$186.85	$186.80
Purchase #7	$83.70	4.858%	$87.7661	$87.77	$87.75	$87.80
7 purchase totals =	$1,002.77		$1,086.9833	$1,086.98	$1,087.00	$1,087.00