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	$181.28	8.406%	$196.5184	$196.52	$196.50	$196.50
Purchase #2	$81.91	9.735%	$89.8839	$89.88	$89.90	$89.90
Purchase #3	$123.82	10.124%	$136.3555	$136.36	$136.35	$136.40
Purchase #4	$158.51	10.301%	$174.8381	$174.84	$174.85	$174.80
Purchase #5	$199.42	4.273%	$207.9412	$207.94	$207.95	$207.90
Purchase #6	$163.97	5.157%	$172.4259	$172.43	$172.45	$172.40
Purchase #7	$244.57	3.843%	$253.9688	$253.97	$253.95	$254.00
7 purchase totals =	$1,153.48		$1,231.9318	$1,231.94	$1,231.95	$1,231.90