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	$31.47	7.204%	$33.7371	$33.74	$33.75	$33.70
Purchase #2	$238.29	8.299%	$258.0657	$258.07	$258.05	$258.10
Purchase #3	$121.93	9.529%	$133.5487	$133.55	$133.55	$133.50
Purchase #4	$52.57	13.260%	$59.5408	$59.54	$59.55	$59.50
Purchase #5	$77.94	9.651%	$85.462	$85.46	$85.45	$85.50
Purchase #6	$13.78	9.256%	$15.0555	$15.06	$15.05	$15.10
Purchase #7	$112.69	3.769%	$116.9373	$116.94	$116.95	$116.90
7 purchase totals =	$648.67		$702.3471	$702.36	$702.35	$702.30