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 $54.54   13.740%   $62.0338   $62.03   $62.05   $62.00  
  Purchase #2 $174.41   3.705%   $180.8719   $180.87   $180.85   $180.90  
  Purchase #3 $191.55   5.434%   $201.9588   $201.96   $201.95   $202.00  
  Purchase #4 $154.32   10.197%   $170.056   $170.06   $170.05   $170.10  
  Purchase #5 $115.47   8.647%   $125.4547   $125.45   $125.45   $125.50  
  Purchase #6 $187.54   11.816%   $209.6997   $209.70   $209.70   $209.70  
  Purchase #7 $231.54   6.626%   $246.8818   $246.88   $246.90   $246.90  
  7 purchase totals = $1,109.37       $1,196.9567   $1,196.95   $1,196.95   $1,197.10