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	$37.93	9.576%	$41.5622	$41.56	$41.55	$41.60
Purchase #2	$163.76	12.309%	$183.9172	$183.92	$183.90	$183.90
Purchase #3	$57.52	3.815%	$59.7144	$59.71	$59.70	$59.70
Purchase #4	$89.32	12.854%	$100.8012	$100.80	$100.80	$100.80
Purchase #5	$164.29	9.160%	$179.339	$179.34	$179.35	$179.30
Purchase #6	$44.53	12.422%	$50.0615	$50.06	$50.05	$50.10
Purchase #7	$197.64	9.586%	$216.5858	$216.59	$216.60	$216.60
7 purchase totals =	$754.99		$831.9813	$831.98	$831.95	$832.00