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	$248.81	13.619%	$282.6954	$282.70	$282.70	$282.70
Purchase #2	$24.73	12.619%	$27.8507	$27.85	$27.85	$27.90
Purchase #3	$150.94	6.602%	$160.9051	$160.91	$160.90	$160.90
Purchase #4	$244.66	9.330%	$267.4868	$267.49	$267.50	$267.50
Purchase #5	$133.94	10.666%	$148.226	$148.23	$148.25	$148.20
Purchase #6	$185.80	5.859%	$196.686	$196.69	$196.70	$196.70
Purchase #7	$29.94	5.526%	$31.5945	$31.59	$31.60	$31.60
7 purchase totals =	$1,018.82		$1,115.4445	$1,115.46	$1,115.50	$1,115.50