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	$56.76	10.772%	$62.8742	$62.87	$62.85	$62.90
Purchase #2	$216.44	5.477%	$228.2944	$228.29	$228.30	$228.30
Purchase #3	$210.70	13.848%	$239.8777	$239.88	$239.90	$239.90
Purchase #4	$113.40	4.862%	$118.9135	$118.91	$118.90	$118.90
Purchase #5	$30.81	10.467%	$34.0349	$34.03	$34.05	$34.00
Purchase #6	$192.96	13.442%	$218.8977	$218.90	$218.90	$218.90
Purchase #7	$95.99	4.867%	$100.6618	$100.66	$100.65	$100.70
7 purchase totals =	$917.06		$1,003.5542	$1,003.54	$1,003.55	$1,003.60