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	$243.73	6.300%	$259.085	$259.09	$259.10	$259.10
Purchase #2	$44.33	13.660%	$50.3855	$50.39	$50.40	$50.40
Purchase #3	$241.89	8.525%	$262.5111	$262.51	$262.50	$262.50
Purchase #4	$112.40	9.764%	$123.3747	$123.37	$123.35	$123.40
Purchase #5	$114.81	3.248%	$118.539	$118.54	$118.55	$118.50
Purchase #6	$35.61	9.165%	$38.8737	$38.87	$38.85	$38.90
Purchase #7	$242.86	7.235%	$260.4309	$260.43	$260.45	$260.40
7 purchase totals =	$1,035.63		$1,113.1999	$1,113.20	$1,113.20	$1,113.20