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	$14.26	8.752%	$15.508	$15.51	$15.50	$15.50
Purchase #2	$241.63	9.334%	$264.1837	$264.18	$264.20	$264.20
Purchase #3	$115.35	13.748%	$131.2083	$131.21	$131.20	$131.20
Purchase #4	$150.33	10.126%	$165.5524	$165.55	$165.55	$165.60
Purchase #5	$219.57	8.533%	$238.3059	$238.31	$238.30	$238.30
Purchase #6	$108.87	4.340%	$113.595	$113.60	$113.60	$113.60
Purchase #7	$137.59	7.278%	$147.6038	$147.60	$147.60	$147.60
7 purchase totals =	$987.60		$1,075.9571	$1,075.96	$1,075.95	$1,076.00