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 $71.93   5.817%   $76.1142   $76.11   $76.10   $76.10  
  Purchase #2 $196.77   7.570%   $211.6655   $211.67   $211.65   $211.70  
  Purchase #3 $89.32   4.516%   $93.3537   $93.35   $93.35   $93.40  
  Purchase #4 $176.84   3.849%   $183.6466   $183.65   $183.65   $183.60  
  Purchase #5 $118.47   5.782%   $125.3199   $125.32   $125.30   $125.30  
  Purchase #6 $56.29   3.768%   $58.411   $58.41   $58.40   $58.40  
  Purchase #7 $156.97   12.112%   $175.9822   $175.98   $176.00   $176.00  
  7 purchase totals = $866.59       $924.4931   $924.49   $924.45   $924.50