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	$22.42	11.391%	$24.9739	$24.97	$24.95	$25.00
Purchase #2	$157.96	10.122%	$173.9487	$173.95	$173.95	$173.90
Purchase #3	$239.68	13.678%	$272.4634	$272.46	$272.45	$272.50
Purchase #4	$79.50	7.565%	$85.5142	$85.51	$85.50	$85.50
Purchase #5	$6.83	12.657%	$7.6945	$7.69	$7.70	$7.70
Purchase #6	$114.56	11.675%	$127.9349	$127.93	$127.95	$127.90
Purchase #7	$165.63	3.281%	$171.0643	$171.06	$171.05	$171.10
7 purchase totals =	$786.58		$863.5939	$863.57	$863.55	$863.60