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 $86.78   8.782%   $94.401   $94.40   $94.40   $94.40  
  Purchase #2 $165.66   3.502%   $171.4614   $171.46   $171.45   $171.50  
  Purchase #3 $115.58   10.195%   $127.3634   $127.36   $127.35   $127.40  
  Purchase #4 $166.33   12.274%   $186.7453   $186.75   $186.75   $186.70  
  Purchase #5 $167.27   13.398%   $189.6808   $189.68   $189.70   $189.70  
  Purchase #6 $212.75   7.834%   $229.4168   $229.42   $229.40   $229.40  
  Purchase #7 $187.32   10.576%   $207.131   $207.13   $207.15   $207.10  
  7 purchase totals = $1,101.69       $1,206.1997   $1,206.20   $1,206.20   $1,206.20