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	$68.55	5.277%	$72.1674	$72.17	$72.15	$72.20
Purchase #2	$146.92	3.396%	$151.9094	$151.91	$151.90	$151.90
Purchase #3	$167.59	5.552%	$176.8946	$176.89	$176.90	$176.90
Purchase #4	$213.48	13.161%	$241.5761	$241.58	$241.60	$241.60
Purchase #5	$184.63	13.168%	$208.9421	$208.94	$208.95	$208.90
Purchase #6	$80.37	11.811%	$89.8625	$89.86	$89.85	$89.90
Purchase #7	$168.58	9.646%	$184.8412	$184.84	$184.85	$184.80
7 purchase totals =	$1,030.12		$1,126.1933	$1,126.19	$1,126.20	$1,126.20