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	$90.76	4.676%	$95.0039	$95.00	$95.00	$95.00
Purchase #2	$151.58	11.455%	$168.9435	$168.94	$168.95	$168.90
Purchase #3	$165.33	4.293%	$172.4276	$172.43	$172.45	$172.40
Purchase #4	$139.59	11.649%	$155.8508	$155.85	$155.85	$155.90
Purchase #5	$242.40	12.611%	$272.9691	$272.97	$272.95	$273.00
Purchase #6	$87.59	3.213%	$90.4043	$90.40	$90.40	$90.40
Purchase #7	$169.79	9.448%	$185.8318	$185.83	$185.85	$185.80
7 purchase totals =	$1,047.04		$1,141.4310	$1,141.42	$1,141.45	$1,141.40