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	$82.98	5.549%	$87.5846	$87.58	$87.60	$87.60
Purchase #2	$145.85	7.570%	$156.8908	$156.89	$156.90	$156.90
Purchase #3	$180.37	3.360%	$186.4304	$186.43	$186.45	$186.40
Purchase #4	$136.43	10.343%	$150.541	$150.54	$150.55	$150.50
Purchase #5	$207.57	3.738%	$215.329	$215.33	$215.35	$215.30
Purchase #6	$217.98	10.141%	$240.0854	$240.09	$240.10	$240.10
Purchase #7	$109.62	12.416%	$123.2304	$123.23	$123.25	$123.20
7 purchase totals =	$1,080.80		$1,160.0916	$1,160.09	$1,160.20	$1,160.00