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	$100.38	5.561%	$105.9621	$105.96	$105.95	$106.00
Purchase #2	$126.39	12.588%	$142.3	$142.30	$142.30	$142.30
Purchase #3	$40.69	11.768%	$45.4784	$45.48	$45.50	$45.50
Purchase #4	$158.34	3.661%	$164.1368	$164.14	$164.15	$164.10
Purchase #5	$163.98	8.221%	$177.4608	$177.46	$177.45	$177.50
Purchase #6	$207.25	8.320%	$224.4932	$224.49	$224.50	$224.50
Purchase #7	$63.63	6.307%	$67.6431	$67.64	$67.65	$67.60
7 purchase totals =	$860.66		$927.4744	$927.47	$927.50	$927.50