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	$227.78	4.397%	$237.7955	$237.80	$237.80	$237.80
Purchase #2	$169.83	8.521%	$184.3012	$184.30	$184.30	$184.30
Purchase #3	$180.78	8.150%	$195.5136	$195.51	$195.50	$195.50
Purchase #4	$161.43	11.141%	$179.4149	$179.41	$179.40	$179.40
Purchase #5	$248.55	11.286%	$276.6014	$276.60	$276.60	$276.60
Purchase #6	$44.83	4.542%	$46.8662	$46.87	$46.85	$46.90
Purchase #7	$69.90	11.601%	$78.0091	$78.01	$78.00	$78.00
7 purchase totals =	$1,103.10		$1,198.5019	$1,198.50	$1,198.45	$1,198.50