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	$242.39	7.737%	$261.1437	$261.14	$261.15	$261.10
Purchase #2	$241.90	11.334%	$269.3169	$269.32	$269.30	$269.30
Purchase #3	$61.72	12.636%	$69.5189	$69.52	$69.50	$69.50
Purchase #4	$213.59	6.412%	$227.2854	$227.29	$227.30	$227.30
Purchase #5	$195.89	10.709%	$216.8679	$216.87	$216.85	$216.90
Purchase #6	$176.37	13.736%	$200.5962	$200.60	$200.60	$200.60
Purchase #7	$73.82	12.824%	$83.2867	$83.29	$83.30	$83.30
7 purchase totals =	$1,205.68		$1,328.0157	$1,328.03	$1,328.00	$1,328.00