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 $173.60   11.713%   $193.9338   $193.93   $193.95   $193.90  
  Purchase #2 $213.89   6.131%   $227.0036   $227.00   $227.00   $227.00  
  Purchase #3 $12.53   11.625%   $13.9866   $13.99   $14.00   $14.00  
  Purchase #4 $59.80   9.791%   $65.655   $65.66   $65.65   $65.70  
  Purchase #5 $123.38   10.226%   $135.9968   $136.00   $136.00   $136.00  
  Purchase #6 $181.48   13.443%   $205.8764   $205.88   $205.90   $205.90  
  Purchase #7 $113.82   5.851%   $120.4796   $120.48   $120.50   $120.50  
  7 purchase totals = $878.50       $962.9318   $962.94   $963.00   $963.00