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	$224.76	7.622%	$241.8912	$241.89	$241.90	$241.90
Purchase #2	$206.43	7.251%	$221.3982	$221.40	$221.40	$221.40
Purchase #3	$196.50	13.189%	$222.4164	$222.42	$222.40	$222.40
Purchase #4	$164.43	9.634%	$180.2712	$180.27	$180.25	$180.30
Purchase #5	$215.69	12.826%	$243.3544	$243.35	$243.35	$243.40
Purchase #6	$204.60	3.606%	$211.9779	$211.98	$212.00	$212.00
Purchase #7	$211.85	13.242%	$239.9032	$239.90	$239.90	$239.90
7 purchase totals =	$1,424.26		$1,561.2125	$1,561.21	$1,561.20	$1,561.30