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	$48.94	12.238%	$54.9293	$54.93	$54.95	$54.90
Purchase #2	$25.68	13.593%	$29.1707	$29.17	$29.15	$29.20
Purchase #3	$77.44	11.665%	$86.4734	$86.47	$86.45	$86.50
Purchase #4	$22.37	8.693%	$24.3146	$24.31	$24.30	$24.30
Purchase #5	$228.95	5.354%	$241.208	$241.21	$241.20	$241.20
Purchase #6	$80.55	12.715%	$90.7919	$90.79	$90.80	$90.80
Purchase #7	$82.48	5.285%	$86.8391	$86.84	$86.85	$86.80
7 purchase totals =	$566.41		$613.7270	$613.72	$613.70	$613.70