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	$29.87	8.410%	$32.3821	$32.38	$32.40	$32.40
Purchase #2	$215.83	12.519%	$242.8498	$242.85	$242.85	$242.80
Purchase #3	$48.61	13.854%	$55.3444	$55.34	$55.35	$55.30
Purchase #4	$62.98	13.296%	$71.3538	$71.35	$71.35	$71.40
Purchase #5	$182.55	5.358%	$192.331	$192.33	$192.35	$192.30
Purchase #6	$6.59	4.747%	$6.9028	$6.90	$6.90	$6.90
Purchase #7	$47.31	9.510%	$51.8092	$51.81	$51.80	$51.80
7 purchase totals =	$593.74		$652.9731	$652.96	$653.00	$652.90