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	$93.99	13.422%	$106.6053	$106.61	$106.60	$106.60
Purchase #2	$19.53	5.732%	$20.6495	$20.65	$20.65	$20.60
Purchase #3	$118.35	7.608%	$127.3541	$127.35	$127.35	$127.40
Purchase #4	$180.66	8.600%	$196.1968	$196.20	$196.20	$196.20
Purchase #5	$35.47	11.201%	$39.443	$39.44	$39.45	$39.40
Purchase #6	$32.31	11.275%	$35.953	$35.95	$35.95	$36.00
Purchase #7	$113.38	9.604%	$124.269	$124.27	$124.25	$124.30
7 purchase totals =	$593.69		$650.4707	$650.47	$650.45	$650.50