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 $87.28   11.144%   $97.0065   $97.01   $97.00   $97.00  
  Purchase #2 $183.39   7.389%   $196.9407   $196.94   $196.95   $196.90  
  Purchase #3 $187.28   7.354%   $201.0526   $201.05   $201.05   $201.10  
  Purchase #4 $98.63   13.347%   $111.7941   $111.79   $111.80   $111.80  
  Purchase #5 $121.55   4.416%   $126.9176   $126.92   $126.90   $126.90  
  Purchase #6 $250.64   6.544%   $267.0419   $267.04   $267.05   $267.00  
  Purchase #7 $140.68   6.562%   $149.9114   $149.91   $149.90   $149.90  
  7 purchase totals = $1,069.45       $1,150.6648   $1,150.66   $1,150.65   $1,150.60