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	$164.51	10.288%	$181.4348	$181.43	$181.45	$181.40
Purchase #2	$213.30	13.239%	$241.5388	$241.54	$241.55	$241.50
Purchase #3	$168.69	13.824%	$192.0097	$192.01	$192.00	$192.00
Purchase #4	$94.51	12.445%	$106.2718	$106.27	$106.25	$106.30
Purchase #5	$31.71	5.832%	$33.5593	$33.56	$33.55	$33.60
Purchase #6	$76.78	6.864%	$82.0502	$82.05	$82.05	$82.10
Purchase #7	$121.46	3.426%	$125.6212	$125.62	$125.60	$125.60
7 purchase totals =	$870.96		$962.4858	$962.48	$962.45	$962.50