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	$123.25	3.469%	$127.5255	$127.53	$127.55	$127.50
Purchase #2	$127.99	8.658%	$139.0714	$139.07	$139.05	$139.10
Purchase #3	$139.53	10.278%	$153.8709	$153.87	$153.85	$153.90
Purchase #4	$138.86	4.468%	$145.0643	$145.06	$145.05	$145.10
Purchase #5	$157.45	11.371%	$175.3536	$175.35	$175.35	$175.40
Purchase #6	$81.92	13.179%	$92.7162	$92.72	$92.70	$92.70
Purchase #7	$232.90	11.576%	$259.8605	$259.86	$259.85	$259.90
7 purchase totals =	$1,001.90		$1,093.4624	$1,093.46	$1,093.40	$1,093.60