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	$247.60	10.116%	$272.6472	$272.65	$272.65	$272.60
Purchase #2	$87.31	12.472%	$98.1993	$98.20	$98.20	$98.20
Purchase #3	$133.99	4.181%	$139.5921	$139.59	$139.60	$139.60
Purchase #4	$64.68	6.401%	$68.8202	$68.82	$68.80	$68.80
Purchase #5	$87.98	3.312%	$90.8939	$90.89	$90.90	$90.90
Purchase #6	$104.99	13.625%	$119.2949	$119.29	$119.30	$119.30
Purchase #7	$232.46	10.290%	$256.3801	$256.38	$256.40	$256.40
7 purchase totals =	$959.01		$1,045.8277	$1,045.82	$1,045.85	$1,045.80