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	$94.89	13.342%	$107.5502	$107.55	$107.55	$107.60
Purchase #2	$54.31	8.659%	$59.0127	$59.01	$59.00	$59.00
Purchase #3	$57.49	7.735%	$61.9369	$61.94	$61.95	$61.90
Purchase #4	$196.72	10.255%	$216.8936	$216.89	$216.90	$216.90
Purchase #5	$146.69	9.490%	$160.6109	$160.61	$160.60	$160.60
Purchase #6	$81.51	6.233%	$86.5905	$86.59	$86.60	$86.60
Purchase #7	$234.92	4.804%	$246.2056	$246.21	$246.20	$246.20
7 purchase totals =	$866.53		$938.8004	$938.80	$938.80	$938.80