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	$114.91	7.729%	$123.7914	$123.79	$123.80	$123.80
Purchase #2	$29.89	9.124%	$32.6172	$32.62	$32.60	$32.60
Purchase #3	$219.65	4.173%	$228.816	$228.82	$228.80	$228.80
Purchase #4	$84.60	4.509%	$88.4146	$88.41	$88.40	$88.40
Purchase #5	$83.86	13.607%	$95.2708	$95.27	$95.25	$95.30
Purchase #6	$13.65	3.858%	$14.1766	$14.18	$14.20	$14.20
Purchase #7	$43.87	5.854%	$46.4381	$46.44	$46.45	$46.40
7 purchase totals =	$590.43		$629.5247	$629.53	$629.50	$629.50