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 $36.49   5.640%   $38.548   $38.55   $38.55   $38.50  
  Purchase #2 $138.91   11.187%   $154.4499   $154.45   $154.45   $154.40  
  Purchase #3 $95.50   5.857%   $101.0934   $101.09   $101.10   $101.10  
  Purchase #4 $182.98   9.854%   $201.0108   $201.01   $201.00   $201.00  
  Purchase #5 $123.46   3.394%   $127.6502   $127.65   $127.65   $127.70  
  Purchase #6 $166.75   8.419%   $180.7887   $180.79   $180.80   $180.80  
  Purchase #7 $207.77   11.843%   $232.3762   $232.38   $232.40   $232.40  
  7 purchase totals = $951.86       $1,035.9172   $1,035.92   $1,035.95   $1,035.90