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 $88.79   7.595%   $95.5336   $95.53   $95.55   $95.50  
  Purchase #2 $59.41   12.248%   $66.6865   $66.69   $66.70   $66.70  
  Purchase #3 $236.81   11.442%   $263.9058   $263.91   $263.90   $263.90  
  Purchase #4 $127.62   6.370%   $135.7494   $135.75   $135.75   $135.70  
  Purchase #5 $16.56   12.216%   $18.583   $18.58   $18.60   $18.60  
  Purchase #6 $237.55   13.332%   $269.2202   $269.22   $269.20   $269.20  
  Purchase #7 $166.83   6.208%   $177.1868   $177.19   $177.20   $177.20  
  7 purchase totals = $933.57       $1,026.8653   $1,026.87   $1,026.90   $1,026.80