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	$123.47	11.425%	$137.5764	$137.58	$137.60	$137.60
Purchase #2	$90.93	5.297%	$95.7466	$95.75	$95.75	$95.70
Purchase #3	$215.25	4.721%	$225.412	$225.41	$225.40	$225.40
Purchase #4	$142.99	9.426%	$156.4682	$156.47	$156.45	$156.50
Purchase #5	$164.54	4.782%	$172.4083	$172.41	$172.40	$172.40
Purchase #6	$138.95	4.102%	$144.6497	$144.65	$144.65	$144.60
Purchase #7	$167.66	10.690%	$185.5829	$185.58	$185.60	$185.60
7 purchase totals =	$1,043.79		$1,117.8441	$1,117.85	$1,117.85	$1,117.80