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	$226.41	11.472%	$252.3838	$252.38	$252.40	$252.40
Purchase #2	$20.37	4.708%	$21.329	$21.33	$21.35	$21.30
Purchase #3	$224.73	6.247%	$238.7689	$238.77	$238.75	$238.80
Purchase #4	$90.78	4.544%	$94.905	$94.91	$94.90	$94.90
Purchase #5	$157.57	7.193%	$168.904	$168.90	$168.90	$168.90
Purchase #6	$112.32	13.337%	$127.3001	$127.30	$127.30	$127.30
Purchase #7	$241.57	12.473%	$271.701	$271.70	$271.70	$271.70
7 purchase totals =	$1,073.75		$1,175.2918	$1,175.29	$1,175.30	$1,175.30