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	$130.31	8.566%	$141.4724	$141.47	$141.45	$141.50
Purchase #2	$49.33	7.172%	$52.8679	$52.87	$52.85	$52.90
Purchase #3	$175.94	10.181%	$193.8525	$193.85	$193.85	$193.90
Purchase #4	$119.45	6.600%	$127.3337	$127.33	$127.35	$127.30
Purchase #5	$140.35	13.445%	$159.2201	$159.22	$159.20	$159.20
Purchase #6	$242.54	13.626%	$275.5885	$275.59	$275.60	$275.60
Purchase #7	$60.43	10.738%	$66.919	$66.92	$66.90	$66.90
7 purchase totals =	$918.35		$1,017.2541	$1,017.25	$1,017.20	$1,017.30