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	$120.47	4.170%	$125.4936	$125.49	$125.50	$125.50
Purchase #2	$207.95	5.135%	$218.6282	$218.63	$218.65	$218.60
Purchase #3	$231.36	10.819%	$256.3908	$256.39	$256.40	$256.40
Purchase #4	$102.54	13.267%	$116.144	$116.14	$116.15	$116.10
Purchase #5	$137.82	8.859%	$150.0295	$150.03	$150.05	$150.00
Purchase #6	$36.31	13.672%	$41.2743	$41.27	$41.25	$41.30
Purchase #7	$31.84	5.540%	$33.6039	$33.60	$33.60	$33.60
7 purchase totals =	$868.29		$941.5643	$941.55	$941.60	$941.50