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 $188.92   3.240%   $195.041   $195.04   $195.05   $195.00  
  Purchase #2 $69.39   8.314%   $75.1591   $75.16   $75.15   $75.20  
  Purchase #3 $112.62   13.283%   $127.5793   $127.58   $127.60   $127.60  
  Purchase #4 $157.63   12.721%   $177.6821   $177.68   $177.70   $177.70  
  Purchase #5 $248.51   8.845%   $270.4907   $270.49   $270.50   $270.50  
  Purchase #6 $191.65   5.172%   $201.5621   $201.56   $201.55   $201.60  
  Purchase #7 $59.94   10.768%   $66.3943   $66.39   $66.40   $66.40  
  7 purchase totals = $1,028.66       $1,113.9086   $1,113.90   $1,113.95   $1,114.00