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	$53.78	3.849%	$55.85	$55.85	$55.85	$55.90
Purchase #2	$38.76	8.615%	$42.0992	$42.10	$42.10	$42.10
Purchase #3	$186.75	3.212%	$192.7484	$192.75	$192.75	$192.70
Purchase #4	$234.54	9.584%	$257.0183	$257.02	$257.00	$257.00
Purchase #5	$74.95	10.636%	$82.9217	$82.92	$82.90	$82.90
Purchase #6	$131.43	4.164%	$136.9027	$136.90	$136.90	$136.90
Purchase #7	$233.99	12.810%	$263.9641	$263.96	$263.95	$264.00
7 purchase totals =	$954.20		$1,031.5044	$1,031.50	$1,031.45	$1,031.50