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	$144.46	4.848%	$151.4634	$151.46	$151.45	$151.50
Purchase #2	$215.94	10.848%	$239.3652	$239.37	$239.35	$239.40
Purchase #3	$33.63	6.661%	$35.8701	$35.87	$35.85	$35.90
Purchase #4	$112.78	5.365%	$118.8306	$118.83	$118.85	$118.80
Purchase #5	$196.74	6.189%	$208.9162	$208.92	$208.90	$208.90
Purchase #6	$80.59	12.854%	$90.949	$90.95	$90.95	$90.90
Purchase #7	$228.65	11.867%	$255.7839	$255.78	$255.80	$255.80
7 purchase totals =	$1,012.79		$1,101.1784	$1,101.18	$1,101.15	$1,101.20