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	$72.47	13.523%	$82.2701	$82.27	$82.25	$82.30
Purchase #2	$134.48	13.348%	$152.4304	$152.43	$152.45	$152.40
Purchase #3	$146.84	13.854%	$167.1832	$167.18	$167.20	$167.20
Purchase #4	$90.75	5.384%	$95.636	$95.64	$95.65	$95.60
Purchase #5	$167.87	10.367%	$185.2731	$185.27	$185.25	$185.30
Purchase #6	$92.45	10.542%	$102.1961	$102.20	$102.20	$102.20
Purchase #7	$117.57	3.176%	$121.304	$121.30	$121.30	$121.30
7 purchase totals =	$822.43		$906.2929	$906.29	$906.30	$906.30