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	$244.78	6.799%	$261.4226	$261.42	$261.40	$261.40
Purchase #2	$203.69	10.444%	$224.9634	$224.96	$224.95	$225.00
Purchase #3	$25.35	8.174%	$27.4221	$27.42	$27.40	$27.40
Purchase #4	$220.34	3.443%	$227.9263	$227.93	$227.95	$227.90
Purchase #5	$53.83	11.187%	$59.852	$59.85	$59.85	$59.90
Purchase #6	$71.93	8.457%	$78.0131	$78.01	$78.00	$78.00
Purchase #7	$184.96	7.504%	$198.8394	$198.84	$198.85	$198.80
7 purchase totals =	$1,004.88		$1,078.4389	$1,078.43	$1,078.40	$1,078.40