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	$126.63	11.645%	$141.3761	$141.38	$141.40	$141.40
Purchase #2	$172.83	13.471%	$196.1119	$196.11	$196.10	$196.10
Purchase #3	$72.37	8.243%	$78.3355	$78.34	$78.35	$78.30
Purchase #4	$228.95	5.145%	$240.7295	$240.73	$240.75	$240.70
Purchase #5	$246.81	10.540%	$272.8238	$272.82	$272.80	$272.80
Purchase #6	$24.63	10.553%	$27.2292	$27.23	$27.25	$27.20
Purchase #7	$224.53	7.352%	$241.0374	$241.04	$241.05	$241.00
7 purchase totals =	$1,096.75		$1,197.6434	$1,197.65	$1,197.70	$1,197.50