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 $84.48   13.216%   $95.6449   $95.64   $95.65   $95.60  
  Purchase #2 $46.40   9.812%   $50.9528   $50.95   $50.95   $51.00  
  Purchase #3 $152.42   12.240%   $171.0762   $171.08   $171.10   $171.10  
  Purchase #4 $196.99   13.477%   $223.5383   $223.54   $223.55   $223.50  
  Purchase #5 $12.78   4.275%   $13.3263   $13.33   $13.35   $13.30  
  Purchase #6 $34.77   4.219%   $36.2369   $36.24   $36.25   $36.20  
  Purchase #7 $194.72   4.640%   $203.755   $203.76   $203.75   $203.80  
  7 purchase totals = $722.56       $794.5304   $794.54   $794.60   $794.50