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	$102.50	13.660%	$116.5015	$116.50	$116.50	$116.50
Purchase #2	$117.30	5.531%	$123.7879	$123.79	$123.80	$123.80
Purchase #3	$37.50	7.866%	$40.4498	$40.45	$40.45	$40.40
Purchase #4	$37.38	9.148%	$40.7995	$40.80	$40.80	$40.80
Purchase #5	$40.31	10.253%	$44.443	$44.44	$44.45	$44.40
Purchase #6	$151.76	7.562%	$163.2361	$163.24	$163.25	$163.20
Purchase #7	$196.89	7.833%	$212.3124	$212.31	$212.30	$212.30
7 purchase totals =	$683.64		$741.5302	$741.53	$741.55	$741.40