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	$139.63	12.405%	$156.9511	$156.95	$156.95	$157.00
Purchase #2	$173.59	13.732%	$197.4274	$197.43	$197.45	$197.40
Purchase #3	$200.30	8.573%	$217.4717	$217.47	$217.45	$217.50
Purchase #4	$76.57	11.750%	$85.567	$85.57	$85.55	$85.60
Purchase #5	$116.26	13.171%	$131.5726	$131.57	$131.55	$131.60
Purchase #6	$31.85	3.582%	$32.9909	$32.99	$33.00	$33.00
Purchase #7	$247.74	6.824%	$264.6458	$264.65	$264.65	$264.60
7 purchase totals =	$985.94		$1,086.6265	$1,086.63	$1,086.60	$1,086.70