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	$225.88	13.722%	$256.8753	$256.88	$256.90	$256.90
Purchase #2	$53.98	4.605%	$56.4658	$56.47	$56.45	$56.50
Purchase #3	$116.56	7.724%	$125.5631	$125.56	$125.55	$125.60
Purchase #4	$61.63	9.295%	$67.3585	$67.36	$67.35	$67.40
Purchase #5	$89.87	5.691%	$94.9845	$94.98	$95.00	$95.00
Purchase #6	$88.99	12.835%	$100.4119	$100.41	$100.40	$100.40
Purchase #7	$225.31	8.276%	$243.9567	$243.96	$243.95	$244.00
7 purchase totals =	$862.22		$945.6158	$945.62	$945.60	$945.80