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	$146.54	3.288%	$151.3582	$151.36	$151.35	$151.40
Purchase #2	$168.42	6.847%	$179.9517	$179.95	$179.95	$180.00
Purchase #3	$197.83	12.552%	$222.6616	$222.66	$222.65	$222.70
Purchase #4	$171.89	4.517%	$179.6543	$179.65	$179.65	$179.70
Purchase #5	$186.56	11.497%	$208.0088	$208.01	$208.00	$208.00
Purchase #6	$114.29	11.493%	$127.4253	$127.43	$127.45	$127.40
Purchase #7	$164.53	8.223%	$178.0593	$178.06	$178.05	$178.10
7 purchase totals =	$1,150.06		$1,247.1192	$1,247.12	$1,247.10	$1,247.30