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	$123.25	8.659%	$133.9222	$133.92	$133.90	$133.90
Purchase #2	$85.86	7.716%	$92.485	$92.49	$92.50	$92.50
Purchase #3	$162.50	12.525%	$182.8531	$182.85	$182.85	$182.90
Purchase #4	$51.72	12.737%	$58.3076	$58.31	$58.30	$58.30
Purchase #5	$246.60	4.185%	$256.9202	$256.92	$256.90	$256.90
Purchase #6	$161.79	5.671%	$170.9651	$170.97	$170.95	$171.00
Purchase #7	$133.43	7.111%	$142.9182	$142.92	$142.90	$142.90
7 purchase totals =	$965.15		$1,038.3714	$1,038.38	$1,038.30	$1,038.40