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 $69.59   9.238%   $76.0187   $76.02   $76.00   $76.00  
  Purchase #2 $103.94   8.719%   $113.0025   $113.00   $113.00   $113.00  
  Purchase #3 $58.32   3.783%   $60.5262   $60.53   $60.55   $60.50  
  Purchase #4 $100.52   8.223%   $108.7858   $108.79   $108.80   $108.80  
  Purchase #5 $81.77   5.781%   $86.4971   $86.50   $86.50   $86.50  
  Purchase #6 $233.79   3.201%   $241.2736   $241.27   $241.25   $241.30  
  Purchase #7 $222.34   12.671%   $250.5127   $250.51   $250.50   $250.50  
  7 purchase totals = $870.27       $936.6166   $936.62   $936.60   $936.60