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	$203.83	10.256%	$224.7348	$224.73	$224.75	$224.70
Purchase #2	$89.42	5.551%	$94.3837	$94.38	$94.40	$94.40
Purchase #3	$122.39	7.822%	$131.9633	$131.96	$131.95	$132.00
Purchase #4	$155.38	4.606%	$162.5368	$162.54	$162.55	$162.50
Purchase #5	$116.38	13.354%	$131.9214	$131.92	$131.90	$131.90
Purchase #6	$246.39	5.561%	$260.0917	$260.09	$260.10	$260.10
Purchase #7	$234.55	11.345%	$261.1597	$261.16	$261.15	$261.20
7 purchase totals =	$1,168.34		$1,266.7914	$1,266.78	$1,266.80	$1,266.80