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	$217.99	13.582%	$247.5974	$247.60	$247.60	$247.60
Purchase #2	$218.66	9.218%	$238.8161	$238.82	$238.80	$238.80
Purchase #3	$87.26	4.138%	$90.8708	$90.87	$90.85	$90.90
Purchase #4	$250.80	8.694%	$272.6046	$272.60	$272.60	$272.60
Purchase #5	$220.42	12.566%	$248.118	$248.12	$248.10	$248.10
Purchase #6	$153.89	10.663%	$170.2993	$170.30	$170.30	$170.30
Purchase #7	$98.95	12.745%	$111.5612	$111.56	$111.55	$111.60
7 purchase totals =	$1,247.97		$1,379.8674	$1,379.87	$1,379.80	$1,379.90