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	$13.35	4.451%	$13.9442	$13.94	$13.95	$13.90
Purchase #2	$225.28	7.504%	$242.185	$242.19	$242.20	$242.20
Purchase #3	$144.96	3.620%	$150.2076	$150.21	$150.20	$150.20
Purchase #4	$77.81	6.123%	$82.5743	$82.57	$82.55	$82.60
Purchase #5	$148.85	12.807%	$167.9132	$167.91	$167.90	$167.90
Purchase #6	$77.31	10.274%	$85.2528	$85.25	$85.25	$85.30
Purchase #7	$33.96	7.603%	$36.542	$36.54	$36.55	$36.50
7 purchase totals =	$721.52		$778.6191	$778.61	$778.60	$778.60