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	$201.43	6.496%	$214.5149	$214.51	$214.50	$214.50
Purchase #2	$116.30	13.404%	$131.8889	$131.89	$131.90	$131.90
Purchase #3	$139.65	11.385%	$155.5492	$155.55	$155.55	$155.50
Purchase #4	$130.77	4.692%	$136.9057	$136.91	$136.90	$136.90
Purchase #5	$106.27	10.491%	$117.4188	$117.42	$117.40	$117.40
Purchase #6	$99.93	8.156%	$108.0803	$108.08	$108.10	$108.10
Purchase #7	$7.57	4.676%	$7.924	$7.92	$7.90	$7.90
7 purchase totals =	$801.92		$872.2818	$872.28	$872.25	$872.20