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	$14.64	3.619%	$15.1698	$15.17	$15.15	$15.20
Purchase #2	$31.82	11.363%	$35.4357	$35.44	$35.45	$35.40
Purchase #3	$143.73	8.676%	$156.2	$156.20	$156.20	$156.20
Purchase #4	$136.96	3.262%	$141.4276	$141.43	$141.45	$141.40
Purchase #5	$188.80	3.861%	$196.0896	$196.09	$196.10	$196.10
Purchase #6	$74.77	3.871%	$77.6643	$77.66	$77.65	$77.70
Purchase #7	$83.58	10.527%	$92.3785	$92.38	$92.40	$92.40
7 purchase totals =	$674.30		$714.3655	$714.37	$714.40	$714.40