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	$125.51	4.762%	$131.4868	$131.49	$131.50	$131.50
Purchase #2	$27.98	11.558%	$31.2139	$31.21	$31.20	$31.20
Purchase #3	$234.62	7.570%	$252.3807	$252.38	$252.40	$252.40
Purchase #4	$139.90	7.493%	$150.3827	$150.38	$150.40	$150.40
Purchase #5	$45.61	6.543%	$48.5943	$48.59	$48.60	$48.60
Purchase #6	$64.92	12.870%	$73.2752	$73.28	$73.30	$73.30
Purchase #7	$217.77	4.755%	$228.125	$228.13	$228.15	$228.10
7 purchase totals =	$856.31		$915.4586	$915.46	$915.55	$915.50