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	$13.35	4.461%	$13.9455	$13.95	$13.95	$13.90
Purchase #2	$169.78	8.672%	$184.5033	$184.50	$184.50	$184.50
Purchase #3	$250.95	4.779%	$262.9429	$262.94	$262.95	$262.90
Purchase #4	$168.38	10.695%	$186.3882	$186.39	$186.40	$186.40
Purchase #5	$29.83	9.259%	$32.592	$32.59	$32.60	$32.60
Purchase #6	$45.61	10.297%	$50.3065	$50.31	$50.30	$50.30
Purchase #7	$245.28	5.787%	$259.4744	$259.47	$259.45	$259.50
7 purchase totals =	$923.18		$990.1528	$990.15	$990.15	$990.10