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 $190.56   7.577%   $204.9987   $205.00   $205.00   $205.00  
  Purchase #2 $41.35   9.605%   $45.3217   $45.32   $45.30   $45.30  
  Purchase #3 $132.46   6.828%   $141.5044   $141.50   $141.50   $141.50  
  Purchase #4 $45.72   8.664%   $49.6812   $49.68   $49.70   $49.70  
  Purchase #5 $70.85   6.709%   $75.6033   $75.60   $75.60   $75.60  
  Purchase #6 $170.98   6.825%   $182.6494   $182.65   $182.65   $182.60  
  Purchase #7 $174.93   4.178%   $182.2386   $182.24   $182.25   $182.20  
  7 purchase totals = $826.85       $881.9973   $881.99   $882.00   $881.90