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	$173.54	13.303%	$196.626	$196.63	$196.65	$196.60
Purchase #2	$35.66	5.784%	$37.7226	$37.72	$37.70	$37.70
Purchase #3	$13.99	12.387%	$15.7229	$15.72	$15.70	$15.70
Purchase #4	$78.36	9.189%	$85.5605	$85.56	$85.55	$85.60
Purchase #5	$190.99	10.453%	$210.9542	$210.95	$210.95	$211.00
Purchase #6	$77.50	10.443%	$85.5933	$85.59	$85.60	$85.60
Purchase #7	$14.37	5.668%	$15.1845	$15.18	$15.20	$15.20
7 purchase totals =	$584.41		$647.3640	$647.35	$647.35	$647.40