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	$241.39	13.862%	$274.8515	$274.85	$274.85	$274.90
Purchase #2	$87.54	7.846%	$94.4084	$94.41	$94.40	$94.40
Purchase #3	$192.61	10.497%	$212.8283	$212.83	$212.85	$212.80
Purchase #4	$66.34	8.294%	$71.8422	$71.84	$71.85	$71.80
Purchase #5	$81.30	6.250%	$86.3813	$86.38	$86.40	$86.40
Purchase #6	$122.90	3.725%	$127.478	$127.48	$127.50	$127.50
Purchase #7	$226.47	3.516%	$234.4327	$234.43	$234.45	$234.40
7 purchase totals =	$1,018.55		$1,102.2224	$1,102.22	$1,102.30	$1,102.20