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	$63.37	6.703%	$67.6177	$67.62	$67.60	$67.60
Purchase #2	$69.67	13.277%	$78.9201	$78.92	$78.90	$78.90
Purchase #3	$58.96	6.479%	$62.78	$62.78	$62.80	$62.80
Purchase #4	$161.74	11.676%	$180.6248	$180.62	$180.60	$180.60
Purchase #5	$203.99	13.405%	$231.3349	$231.33	$231.35	$231.30
Purchase #6	$142.58	13.792%	$162.2446	$162.24	$162.25	$162.20
Purchase #7	$35.52	8.558%	$38.5598	$38.56	$38.55	$38.60
7 purchase totals =	$735.83		$822.0819	$822.07	$822.05	$822.00