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 $172.49   7.526%   $185.4716   $185.47   $185.45   $185.50  
  Purchase #2 $228.54   6.681%   $243.8088   $243.81   $243.80   $243.80  
  Purchase #3 $160.44   6.615%   $171.0531   $171.05   $171.05   $171.10  
  Purchase #4 $27.65   6.229%   $29.3723   $29.37   $29.35   $29.40  
  Purchase #5 $92.53   5.475%   $97.596   $97.60   $97.60   $97.60  
  Purchase #6 $201.75   6.843%   $215.5558   $215.56   $215.55   $215.60  
  Purchase #7 $228.97   13.162%   $259.107   $259.11   $259.10   $259.10  
  7 purchase totals = $1,112.37       $1,201.9646   $1,201.97   $1,201.90   $1,202.10