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	$10.55	7.730%	$11.3655	$11.37	$11.35	$11.40
Purchase #2	$246.78	5.341%	$259.9605	$259.96	$259.95	$260.00
Purchase #3	$120.91	5.248%	$127.2554	$127.26	$127.25	$127.30
Purchase #4	$145.93	11.633%	$162.906	$162.91	$162.90	$162.90
Purchase #5	$230.92	13.471%	$262.0272	$262.03	$262.05	$262.00
Purchase #6	$35.50	13.501%	$40.2929	$40.29	$40.30	$40.30
Purchase #7	$194.95	13.112%	$220.5118	$220.51	$220.50	$220.50
7 purchase totals =	$985.54		$1,084.3193	$1,084.33	$1,084.30	$1,084.40