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	$132.84	9.866%	$145.946	$145.95	$145.95	$145.90
Purchase #2	$73.66	11.554%	$82.1707	$82.17	$82.15	$82.20
Purchase #3	$36.89	4.737%	$38.6375	$38.64	$38.65	$38.60
Purchase #4	$36.45	10.579%	$40.306	$40.31	$40.30	$40.30
Purchase #5	$241.46	12.764%	$272.28	$272.28	$272.30	$272.30
Purchase #6	$58.85	6.756%	$62.8259	$62.83	$62.85	$62.80
Purchase #7	$205.71	10.812%	$227.9514	$227.95	$227.95	$228.00
7 purchase totals =	$785.86		$870.1175	$870.13	$870.15	$870.10