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	$173.39	13.320%	$196.4855	$196.49	$196.50	$196.50
Purchase #2	$101.74	3.752%	$105.5573	$105.56	$105.55	$105.60
Purchase #3	$210.30	8.173%	$227.4878	$227.49	$227.50	$227.50
Purchase #4	$199.28	8.132%	$215.4854	$215.49	$215.50	$215.50
Purchase #5	$62.44	6.456%	$66.4711	$66.47	$66.45	$66.50
Purchase #6	$66.88	10.659%	$74.0087	$74.01	$74.00	$74.00
Purchase #7	$52.30	9.820%	$57.4359	$57.44	$57.45	$57.40
7 purchase totals =	$866.33		$942.9317	$942.95	$942.95	$943.00