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 $181.83   10.677%   $201.244   $201.24   $201.25   $201.20  
  Purchase #2 $58.76   5.499%   $61.9912   $61.99   $62.00   $62.00  
  Purchase #3 $106.84   5.351%   $112.557   $112.56   $112.55   $112.60  
  Purchase #4 $17.55   6.110%   $18.6223   $18.62   $18.60   $18.60  
  Purchase #5 $111.92   8.856%   $121.8316   $121.83   $121.85   $121.80  
  Purchase #6 $238.89   3.361%   $246.9191   $246.92   $246.90   $246.90  
  Purchase #7 $231.64   12.401%   $260.3657   $260.37   $260.35   $260.40  
  7 purchase totals = $947.43       $1,023.5309   $1,023.53   $1,023.50   $1,023.50