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	$24.41	9.553%	$26.7419	$26.74	$26.75	$26.70
Purchase #2	$172.83	7.556%	$185.889	$185.89	$185.90	$185.90
Purchase #3	$234.60	4.637%	$245.4784	$245.48	$245.50	$245.50
Purchase #4	$136.59	8.758%	$148.5526	$148.55	$148.55	$148.60
Purchase #5	$160.57	11.798%	$179.514	$179.51	$179.50	$179.50
Purchase #6	$95.29	6.447%	$101.4333	$101.43	$101.45	$101.40
Purchase #7	$107.29	11.679%	$119.8204	$119.82	$119.80	$119.80
7 purchase totals =	$931.58		$1,007.4296	$1,007.42	$1,007.45	$1,007.40