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	$151.36	8.672%	$164.4859	$164.49	$164.50	$164.50
Purchase #2	$172.48	3.868%	$179.1515	$179.15	$179.15	$179.20
Purchase #3	$156.75	9.501%	$171.6428	$171.64	$171.65	$171.60
Purchase #4	$227.32	13.351%	$257.6695	$257.67	$257.65	$257.70
Purchase #5	$188.48	10.419%	$208.1177	$208.12	$208.10	$208.10
Purchase #6	$186.78	11.105%	$207.5219	$207.52	$207.50	$207.50
Purchase #7	$88.35	4.397%	$92.2347	$92.23	$92.25	$92.20
7 purchase totals =	$1,171.52		$1,280.8240	$1,280.82	$1,280.80	$1,280.80