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	$140.76	8.870%	$153.2454	$153.25	$153.25	$153.20
Purchase #2	$86.68	3.240%	$89.4884	$89.49	$89.50	$89.50
Purchase #3	$136.69	3.158%	$141.0067	$141.01	$141.00	$141.00
Purchase #4	$207.39	4.703%	$217.1436	$217.14	$217.15	$217.10
Purchase #5	$108.28	7.395%	$116.2873	$116.29	$116.30	$116.30
Purchase #6	$30.63	10.479%	$33.8397	$33.84	$33.85	$33.80
Purchase #7	$150.51	10.715%	$166.6371	$166.64	$166.65	$166.60
7 purchase totals =	$860.94		$917.6482	$917.66	$917.70	$917.50