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	$68.86	11.722%	$76.9318	$76.93	$76.95	$76.90
Purchase #2	$238.26	13.811%	$271.1661	$271.17	$271.15	$271.20
Purchase #3	$69.60	5.507%	$73.4329	$73.43	$73.45	$73.40
Purchase #4	$126.44	10.311%	$139.4772	$139.48	$139.50	$139.50
Purchase #5	$186.73	12.692%	$210.4298	$210.43	$210.45	$210.40
Purchase #6	$133.43	4.390%	$139.2876	$139.29	$139.30	$139.30
Purchase #7	$125.53	4.851%	$131.6195	$131.62	$131.60	$131.60
7 purchase totals =	$948.85		$1,042.3449	$1,042.35	$1,042.40	$1,042.30