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	$30.29	13.297%	$34.3177	$34.32	$34.30	$34.30
Purchase #2	$167.46	13.798%	$190.5661	$190.57	$190.55	$190.60
Purchase #3	$44.68	8.281%	$48.38	$48.38	$48.40	$48.40
Purchase #4	$43.67	3.137%	$45.0399	$45.04	$45.05	$45.00
Purchase #5	$174.48	5.652%	$184.3416	$184.34	$184.35	$184.30
Purchase #6	$230.43	8.420%	$249.8322	$249.83	$249.85	$249.80
Purchase #7	$240.85	6.320%	$256.0717	$256.07	$256.05	$256.10
7 purchase totals =	$931.86		$1,008.5492	$1,008.55	$1,008.55	$1,008.50