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 $86.69   10.359%   $95.6702   $95.67   $95.65   $95.70  
  Purchase #2 $120.96   13.834%   $137.6936   $137.69   $137.70   $137.70  
  Purchase #3 $27.68   13.661%   $31.4614   $31.46   $31.45   $31.50  
  Purchase #4 $50.36   3.505%   $52.1251   $52.13   $52.15   $52.10  
  Purchase #5 $222.54   8.774%   $242.0657   $242.07   $242.05   $242.10  
  Purchase #6 $246.58   11.257%   $274.3375   $274.34   $274.35   $274.30  
  Purchase #7 $207.60   7.716%   $223.6184   $223.62   $223.60   $223.60  
  7 purchase totals = $962.41       $1,056.9719   $1,056.98   $1,056.95   $1,057.00