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	$34.44	3.742%	$35.7287	$35.73	$35.75	$35.70
Purchase #2	$214.96	12.269%	$241.3334	$241.33	$241.35	$241.30
Purchase #3	$207.38	8.444%	$224.8912	$224.89	$224.90	$224.90
Purchase #4	$222.88	8.796%	$242.4845	$242.48	$242.50	$242.50
Purchase #5	$88.47	13.702%	$100.5922	$100.59	$100.60	$100.60
Purchase #6	$134.77	13.540%	$153.0179	$153.02	$153.00	$153.00
Purchase #7	$18.94	3.677%	$19.6364	$19.64	$19.65	$19.60
7 purchase totals =	$921.84		$1,017.6843	$1,017.68	$1,017.75	$1,017.60