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 $58.33   8.775%   $63.4485   $63.45   $63.45   $63.40  
  Purchase #2 $125.34   6.127%   $133.0196   $133.02   $133.00   $133.00  
  Purchase #3 $52.38   6.651%   $55.8638   $55.86   $55.85   $55.90  
  Purchase #4 $239.72   8.731%   $260.65   $260.65   $260.65   $260.70  
  Purchase #5 $238.31   7.252%   $255.5922   $255.59   $255.60   $255.60  
  Purchase #6 $179.93   9.475%   $196.9784   $196.98   $197.00   $197.00  
  Purchase #7 $128.96   5.236%   $135.7123   $135.71   $135.70   $135.70  
  7 purchase totals = $1,022.97       $1,101.2648   $1,101.26   $1,101.25   $1,101.30