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	$115.71	3.332%	$119.5655	$119.57	$119.55	$119.60
Purchase #2	$109.39	12.673%	$123.253	$123.25	$123.25	$123.30
Purchase #3	$206.65	12.860%	$233.2252	$233.23	$233.25	$233.20
Purchase #4	$82.75	3.433%	$85.5908	$85.59	$85.60	$85.60
Purchase #5	$30.94	12.789%	$34.8969	$34.90	$34.90	$34.90
Purchase #6	$121.44	4.443%	$126.8356	$126.84	$126.85	$126.80
Purchase #7	$35.35	8.462%	$38.3413	$38.34	$38.35	$38.30
7 purchase totals =	$702.23		$761.7083	$761.72	$761.75	$761.70