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	$14.37	3.548%	$14.8798	$14.88	$14.90	$14.90
Purchase #2	$81.29	11.295%	$90.4717	$90.47	$90.45	$90.50
Purchase #3	$87.30	4.457%	$91.191	$91.19	$91.20	$91.20
Purchase #4	$22.75	12.237%	$25.5339	$25.53	$25.55	$25.50
Purchase #5	$208.51	9.284%	$227.8681	$227.87	$227.85	$227.90
Purchase #6	$122.43	13.843%	$139.378	$139.38	$139.40	$139.40
Purchase #7	$187.66	13.791%	$213.5402	$213.54	$213.55	$213.50
7 purchase totals =	$724.31		$802.8627	$802.86	$802.90	$802.90