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	$66.50	9.588%	$72.876	$72.88	$72.90	$72.90
Purchase #2	$68.42	11.549%	$76.3218	$76.32	$76.30	$76.30
Purchase #3	$236.82	10.859%	$262.5363	$262.54	$262.55	$262.50
Purchase #4	$124.90	13.610%	$141.8989	$141.90	$141.90	$141.90
Purchase #5	$215.71	5.623%	$227.8394	$227.84	$227.85	$227.80
Purchase #6	$184.65	7.586%	$198.6575	$198.66	$198.65	$198.70
Purchase #7	$113.45	3.693%	$117.6397	$117.64	$117.65	$117.60
7 purchase totals =	$1,010.45		$1,097.7696	$1,097.78	$1,097.80	$1,097.70