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	$102.51	11.127%	$113.9163	$113.92	$113.90	$113.90
Purchase #2	$51.79	13.204%	$58.6284	$58.63	$58.65	$58.60
Purchase #3	$76.39	13.784%	$86.9196	$86.92	$86.90	$86.90
Purchase #4	$180.38	6.781%	$192.6116	$192.61	$192.60	$192.60
Purchase #5	$145.79	11.467%	$162.5077	$162.51	$162.50	$162.50
Purchase #6	$73.88	6.800%	$78.9038	$78.90	$78.90	$78.90
Purchase #7	$95.32	7.662%	$102.6234	$102.62	$102.60	$102.60
7 purchase totals =	$726.06		$796.1108	$796.11	$796.05	$796.00