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	$164.53	7.420%	$176.7381	$176.74	$176.75	$176.70
Purchase #2	$126.56	13.514%	$143.6633	$143.66	$143.65	$143.70
Purchase #3	$238.26	9.700%	$261.3712	$261.37	$261.35	$261.40
Purchase #4	$78.57	13.856%	$89.4567	$89.46	$89.45	$89.50
Purchase #5	$167.47	6.598%	$178.5197	$178.52	$178.50	$178.50
Purchase #6	$97.96	5.328%	$103.1793	$103.18	$103.20	$103.20
Purchase #7	$150.54	10.651%	$166.574	$166.57	$166.55	$166.60
7 purchase totals =	$1,023.89		$1,119.5023	$1,119.50	$1,119.45	$1,119.60