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	$240.37	5.183%	$252.8284	$252.83	$252.85	$252.80
Purchase #2	$147.34	6.121%	$156.3587	$156.36	$156.35	$156.40
Purchase #3	$63.25	13.462%	$71.7647	$71.76	$71.75	$71.80
Purchase #4	$86.31	4.834%	$90.4822	$90.48	$90.50	$90.50
Purchase #5	$243.93	9.859%	$267.9791	$267.98	$268.00	$268.00
Purchase #6	$24.68	3.389%	$25.5164	$25.52	$25.50	$25.50
Purchase #7	$75.57	8.832%	$82.2443	$82.24	$82.25	$82.20
7 purchase totals =	$881.45		$947.1738	$947.17	$947.20	$947.20