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	$228.81	5.413%	$241.1955	$241.20	$241.20	$241.20
Purchase #2	$232.62	5.797%	$246.105	$246.11	$246.10	$246.10
Purchase #3	$105.51	12.296%	$118.4835	$118.48	$118.50	$118.50
Purchase #4	$13.79	11.109%	$15.3219	$15.32	$15.30	$15.30
Purchase #5	$98.52	13.294%	$111.6172	$111.62	$111.60	$111.60
Purchase #6	$114.39	4.155%	$119.1429	$119.14	$119.15	$119.10
Purchase #7	$99.99	12.321%	$112.3098	$112.31	$112.30	$112.30
7 purchase totals =	$893.63		$964.1758	$964.18	$964.15	$964.10