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	$238.50	8.430%	$258.6056	$258.61	$258.60	$258.60
Purchase #2	$133.48	8.477%	$144.7951	$144.80	$144.80	$144.80
Purchase #3	$201.25	9.339%	$220.0447	$220.04	$220.05	$220.00
Purchase #4	$69.67	13.117%	$78.8086	$78.81	$78.80	$78.80
Purchase #5	$55.43	7.163%	$59.4005	$59.40	$59.40	$59.40
Purchase #6	$81.50	6.252%	$86.5954	$86.60	$86.60	$86.60
Purchase #7	$170.87	6.638%	$182.2124	$182.21	$182.20	$182.20
7 purchase totals =	$950.70		$1,030.4623	$1,030.47	$1,030.45	$1,030.40