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	$194.88	3.605%	$201.9054	$201.91	$201.90	$201.90
Purchase #2	$175.52	13.342%	$198.9379	$198.94	$198.95	$198.90
Purchase #3	$66.30	6.335%	$70.5001	$70.50	$70.50	$70.50
Purchase #4	$76.43	12.404%	$85.9104	$85.91	$85.90	$85.90
Purchase #5	$246.31	10.746%	$272.7785	$272.78	$272.80	$272.80
Purchase #6	$246.51	10.544%	$272.502	$272.50	$272.50	$272.50
Purchase #7	$72.61	7.395%	$77.9795	$77.98	$78.00	$78.00
7 purchase totals =	$1,078.56		$1,180.5138	$1,180.52	$1,180.55	$1,180.50