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	$113.30	5.311%	$119.3174	$119.32	$119.30	$119.30
Purchase #2	$28.45	3.778%	$29.5248	$29.52	$29.50	$29.50
Purchase #3	$207.66	9.604%	$227.6037	$227.60	$227.60	$227.60
Purchase #4	$164.47	4.610%	$172.0521	$172.05	$172.05	$172.10
Purchase #5	$148.59	12.812%	$167.6274	$167.63	$167.65	$167.60
Purchase #6	$224.35	9.840%	$246.426	$246.43	$246.45	$246.40
Purchase #7	$54.66	3.701%	$56.683	$56.68	$56.70	$56.70
7 purchase totals =	$941.48		$1,019.2344	$1,019.23	$1,019.25	$1,019.20