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	$31.38	13.256%	$35.5397	$35.54	$35.55	$35.50
Purchase #2	$180.29	9.507%	$197.4302	$197.43	$197.45	$197.40
Purchase #3	$102.25	9.156%	$111.612	$111.61	$111.60	$111.60
Purchase #4	$175.82	12.763%	$198.2599	$198.26	$198.25	$198.30
Purchase #5	$126.45	6.330%	$134.4543	$134.45	$134.45	$134.50
Purchase #6	$71.89	8.136%	$77.739	$77.74	$77.75	$77.70
Purchase #7	$238.50	4.828%	$250.0148	$250.01	$250.00	$250.00
7 purchase totals =	$926.58		$1,005.0499	$1,005.04	$1,005.05	$1,005.00