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 $119.77   5.665%   $126.555   $126.56   $126.55   $126.60  
  Purchase #2 $74.41   12.250%   $83.5252   $83.53   $83.55   $83.50  
  Purchase #3 $192.35   12.661%   $216.7034   $216.70   $216.70   $216.70  
  Purchase #4 $86.61   6.157%   $91.9426   $91.94   $91.95   $91.90  
  Purchase #5 $57.63   5.662%   $60.893   $60.89   $60.90   $60.90  
  Purchase #6 $204.75   13.596%   $232.5878   $232.59   $232.60   $232.60  
  Purchase #7 $207.75   13.637%   $236.0809   $236.08   $236.10   $236.10  
  7 purchase totals = $943.27       $1,048.2879   $1,048.29   $1,048.35   $1,048.30