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	$160.44	13.605%	$182.2679	$182.27	$182.25	$182.30
Purchase #2	$96.87	8.870%	$105.4624	$105.46	$105.45	$105.50
Purchase #3	$93.39	9.124%	$101.9109	$101.91	$101.90	$101.90
Purchase #4	$135.78	11.114%	$150.8706	$150.87	$150.85	$150.90
Purchase #5	$158.68	8.328%	$171.8949	$171.89	$171.90	$171.90
Purchase #6	$36.59	3.452%	$37.8531	$37.85	$37.85	$37.90
Purchase #7	$208.83	11.207%	$232.2336	$232.23	$232.25	$232.20
7 purchase totals =	$890.58		$982.4934	$982.48	$982.45	$982.60