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	$199.83	3.836%	$207.4955	$207.50	$207.50	$207.50
Purchase #2	$41.43	9.570%	$45.3949	$45.39	$45.40	$45.40
Purchase #3	$65.38	3.500%	$67.6683	$67.67	$67.65	$67.70
Purchase #4	$31.83	8.418%	$34.5094	$34.51	$34.50	$34.50
Purchase #5	$149.43	12.788%	$168.5391	$168.54	$168.55	$168.50
Purchase #6	$97.46	5.721%	$103.0357	$103.04	$103.05	$103.00
Purchase #7	$172.94	13.163%	$195.7041	$195.70	$195.70	$195.70
7 purchase totals =	$758.30		$822.3470	$822.35	$822.35	$822.30