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 $156.26   11.813%   $174.719   $174.72   $174.70   $174.70  
  Purchase #2 $207.63   8.485%   $225.2474   $225.25   $225.25   $225.20  
  Purchase #3 $180.45   5.125%   $189.6981   $189.70   $189.70   $189.70  
  Purchase #4 $135.65   6.853%   $144.9461   $144.95   $144.95   $144.90  
  Purchase #5 $78.30   8.119%   $84.6572   $84.66   $84.65   $84.70  
  Purchase #6 $19.40   10.409%   $21.4193   $21.42   $21.40   $21.40  
  Purchase #7 $192.93   6.141%   $204.7778   $204.78   $204.80   $204.80  
  7 purchase totals = $970.62       $1,045.4649   $1,045.48   $1,045.45   $1,045.40