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	$47.69	4.301%	$49.7411	$49.74	$49.75	$49.70
Purchase #2	$242.73	5.382%	$255.7937	$255.79	$255.80	$255.80
Purchase #3	$69.88	11.259%	$77.7478	$77.75	$77.75	$77.70
Purchase #4	$217.57	10.576%	$240.5802	$240.58	$240.60	$240.60
Purchase #5	$87.44	9.808%	$96.0161	$96.02	$96.00	$96.00
Purchase #6	$225.41	13.280%	$255.3444	$255.34	$255.35	$255.30
Purchase #7	$80.31	7.826%	$86.5951	$86.60	$86.60	$86.60
7 purchase totals =	$971.03		$1,061.8184	$1,061.82	$1,061.85	$1,061.70