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	$177.42	13.634%	$201.6094	$201.61	$201.60	$201.60
Purchase #2	$128.90	12.524%	$145.0434	$145.04	$145.05	$145.00
Purchase #3	$111.29	7.373%	$119.4954	$119.50	$119.50	$119.50
Purchase #4	$28.32	4.111%	$29.4842	$29.48	$29.50	$29.50
Purchase #5	$179.69	4.525%	$187.821	$187.82	$187.80	$187.80
Purchase #6	$155.56	8.566%	$168.8853	$168.89	$168.90	$168.90
Purchase #7	$136.75	11.349%	$152.2698	$152.27	$152.25	$152.30
7 purchase totals =	$917.93		$1,004.6085	$1,004.61	$1,004.60	$1,004.60