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	$7.33	8.330%	$7.9406	$7.94	$7.95	$7.90
Purchase #2	$37.55	7.651%	$40.423	$40.42	$40.40	$40.40
Purchase #3	$116.27	13.471%	$131.9327	$131.93	$131.95	$131.90
Purchase #4	$241.71	5.594%	$255.2313	$255.23	$255.25	$255.20
Purchase #5	$150.82	7.127%	$161.5689	$161.57	$161.55	$161.60
Purchase #6	$69.98	3.855%	$72.6777	$72.68	$72.70	$72.70
Purchase #7	$247.77	9.221%	$270.6169	$270.62	$270.60	$270.60
7 purchase totals =	$871.43		$940.3911	$940.39	$940.40	$940.30