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 $97.86   9.817%   $107.4669   $107.47   $107.45   $107.50  
  Purchase #2 $119.94   9.789%   $131.6809   $131.68   $131.70   $131.70  
  Purchase #3 $43.47   5.776%   $45.9808   $45.98   $46.00   $46.00  
  Purchase #4 $248.58   6.190%   $263.9671   $263.97   $263.95   $264.00  
  Purchase #5 $43.89   4.827%   $46.0086   $46.01   $46.00   $46.00  
  Purchase #6 $134.28   11.821%   $150.1532   $150.15   $150.15   $150.20  
  Purchase #7 $108.39   11.277%   $120.6131   $120.61   $120.60   $120.60  
  7 purchase totals = $796.41       $865.8706   $865.87   $865.85   $866.00