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	$201.28	6.290%	$213.9405	$213.94	$213.95	$213.90
Purchase #2	$194.85	5.490%	$205.5473	$205.55	$205.55	$205.50
Purchase #3	$123.84	6.274%	$131.6097	$131.61	$131.60	$131.60
Purchase #4	$74.41	4.435%	$77.7101	$77.71	$77.70	$77.70
Purchase #5	$163.46	5.438%	$172.349	$172.35	$172.35	$172.30
Purchase #6	$37.87	7.161%	$40.5819	$40.58	$40.60	$40.60
Purchase #7	$90.90	12.505%	$102.267	$102.27	$102.25	$102.30
7 purchase totals =	$886.61		$944.0055	$944.01	$944.00	$943.90