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 $71.88   5.680%   $75.9628   $75.96   $75.95   $76.00  
  Purchase #2 $181.89   11.445%   $202.7073   $202.71   $202.70   $202.70  
  Purchase #3 $108.85   3.737%   $112.9177   $112.92   $112.90   $112.90  
  Purchase #4 $30.28   9.682%   $33.2117   $33.21   $33.20   $33.20  
  Purchase #5 $234.36   6.613%   $249.8582   $249.86   $249.85   $249.90  
  Purchase #6 $24.80   5.650%   $26.2012   $26.20   $26.20   $26.20  
  Purchase #7 $183.86   12.545%   $206.9252   $206.93   $206.95   $206.90  
  7 purchase totals = $835.92       $907.7841   $907.79   $907.75   $907.80