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	$242.27	8.517%	$262.9041	$262.90	$262.90	$262.90
Purchase #2	$246.82	10.712%	$273.2594	$273.26	$273.25	$273.30
Purchase #3	$47.43	4.220%	$49.4315	$49.43	$49.45	$49.40
Purchase #4	$138.89	5.643%	$146.7276	$146.73	$146.75	$146.70
Purchase #5	$99.83	5.578%	$105.3985	$105.40	$105.40	$105.40
Purchase #6	$150.46	6.346%	$160.0082	$160.01	$160.00	$160.00
Purchase #7	$154.71	9.105%	$168.7963	$168.80	$168.80	$168.80
7 purchase totals =	$1,080.41		$1,166.5256	$1,166.53	$1,166.55	$1,166.50