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 $224.27   9.536%   $245.6564   $245.66   $245.65   $245.70  
  Purchase #2 $207.69   13.157%   $235.0158   $235.02   $235.00   $235.00  
  Purchase #3 $82.71   4.207%   $86.1896   $86.19   $86.20   $86.20  
  Purchase #4 $227.93   11.439%   $254.0029   $254.00   $254.00   $254.00  
  Purchase #5 $8.60   13.683%   $9.7767   $9.78   $9.80   $9.80  
  Purchase #6 $68.44   4.579%   $71.5739   $71.57   $71.55   $71.60  
  Purchase #7 $128.30   9.700%   $140.7451   $140.75   $140.75   $140.70  
  7 purchase totals = $947.94       $1,042.9604   $1,042.97   $1,042.95   $1,043.00