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	$237.92	6.862%	$254.2461	$254.25	$254.25	$254.20
Purchase #2	$142.89	10.184%	$157.4419	$157.44	$157.45	$157.40
Purchase #3	$134.34	7.822%	$144.8481	$144.85	$144.85	$144.80
Purchase #4	$186.59	10.804%	$206.7492	$206.75	$206.75	$206.70
Purchase #5	$81.33	11.696%	$90.8424	$90.84	$90.85	$90.80
Purchase #6	$143.78	5.831%	$152.1638	$152.16	$152.15	$152.20
Purchase #7	$114.39	8.153%	$123.7162	$123.72	$123.70	$123.70
7 purchase totals =	$1,041.24		$1,130.0077	$1,130.01	$1,130.00	$1,129.80