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	$230.60	9.801%	$253.2011	$253.20	$253.20	$253.20
Purchase #2	$154.33	3.832%	$160.2439	$160.24	$160.25	$160.20
Purchase #3	$86.82	3.330%	$89.7111	$89.71	$89.70	$89.70
Purchase #4	$19.52	11.293%	$21.7244	$21.72	$21.70	$21.70
Purchase #5	$202.54	12.431%	$227.7177	$227.72	$227.70	$227.70
Purchase #6	$90.57	11.866%	$101.317	$101.32	$101.30	$101.30
Purchase #7	$74.80	9.812%	$82.1394	$82.14	$82.15	$82.10
7 purchase totals =	$859.18		$936.0546	$936.05	$936.00	$935.90