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 $87.31   6.176%   $92.7023   $92.70   $92.70   $92.70  
  Purchase #2 $90.99   6.709%   $97.0945   $97.09   $97.10   $97.10  
  Purchase #3 $24.52   12.843%   $27.6691   $27.67   $27.65   $27.70  
  Purchase #4 $248.67   12.163%   $278.9157   $278.92   $278.90   $278.90  
  Purchase #5 $239.88   13.628%   $272.5708   $272.57   $272.55   $272.60  
  Purchase #6 $194.37   11.475%   $216.674   $216.67   $216.65   $216.70  
  Purchase #7 $70.29   8.785%   $76.465   $76.47   $76.45   $76.50  
  7 purchase totals = $956.03       $1,062.0914   $1,062.09   $1,062.00   $1,062.20