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 $64.73   8.520%   $70.245   $70.25   $70.25   $70.20  
  Purchase #2 $150.54   3.775%   $156.2229   $156.22   $156.20   $156.20  
  Purchase #3 $183.39   12.871%   $206.9941   $206.99   $207.00   $207.00  
  Purchase #4 $215.41   12.701%   $242.7692   $242.77   $242.75   $242.80  
  Purchase #5 $205.89   9.372%   $225.186   $225.19   $225.20   $225.20  
  Purchase #6 $164.92   3.363%   $170.4663   $170.47   $170.45   $170.50  
  Purchase #7 $102.66   3.506%   $106.2593   $106.26   $106.25   $106.30  
  7 purchase totals = $1,087.54       $1,178.1428   $1,178.15   $1,178.10   $1,178.20