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	$194.57	8.451%	$211.0131	$211.01	$211.00	$211.00
Purchase #2	$34.60	7.874%	$37.3244	$37.32	$37.30	$37.30
Purchase #3	$131.78	3.268%	$136.0866	$136.09	$136.10	$136.10
Purchase #4	$214.72	6.776%	$229.2694	$229.27	$229.25	$229.30
Purchase #5	$35.64	10.590%	$39.4143	$39.41	$39.40	$39.40
Purchase #6	$128.82	8.290%	$139.4992	$139.50	$139.50	$139.50
Purchase #7	$57.39	9.583%	$62.8897	$62.89	$62.90	$62.90
7 purchase totals =	$797.52		$855.4967	$855.49	$855.45	$855.50