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	$242.73	5.812%	$256.8375	$256.84	$256.85	$256.80
Purchase #2	$44.34	3.457%	$45.8728	$45.87	$45.85	$45.90
Purchase #3	$190.80	11.843%	$213.3964	$213.40	$213.40	$213.40
Purchase #4	$29.39	10.549%	$32.4904	$32.49	$32.50	$32.50
Purchase #5	$112.77	4.588%	$117.9439	$117.94	$117.95	$117.90
Purchase #6	$113.82	5.325%	$119.8809	$119.88	$119.90	$119.90
Purchase #7	$207.42	9.609%	$227.351	$227.35	$227.35	$227.40
7 purchase totals =	$941.27		$1,013.7729	$1,013.77	$1,013.80	$1,013.80