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 $188.93   6.410%   $201.0404   $201.04   $201.05   $201.00  
  Purchase #2 $56.67   8.709%   $61.6054   $61.61   $61.60   $61.60  
  Purchase #3 $113.37   3.861%   $117.7472   $117.75   $117.75   $117.70  
  Purchase #4 $205.82   10.112%   $226.6325   $226.63   $226.65   $226.60  
  Purchase #5 $48.52   12.750%   $54.7063   $54.71   $54.70   $54.70  
  Purchase #6 $123.81   10.785%   $137.1629   $137.16   $137.15   $137.20  
  Purchase #7 $189.75   10.263%   $209.224   $209.22   $209.20   $209.20  
  7 purchase totals = $926.87       $1,008.1187   $1,008.12   $1,008.10   $1,008.00