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 $207.26   3.754%   $215.0405   $215.04   $215.05   $215.00  
  Purchase #2 $60.62   3.365%   $62.6599   $62.66   $62.65   $62.70  
  Purchase #3 $242.70   11.275%   $270.0644   $270.06   $270.05   $270.10  
  Purchase #4 $67.76   8.763%   $73.6978   $73.70   $73.70   $73.70  
  Purchase #5 $93.42   6.717%   $99.695   $99.70   $99.70   $99.70  
  Purchase #6 $62.29   11.513%   $69.4614   $69.46   $69.45   $69.50  
  Purchase #7 $230.89   10.614%   $255.3967   $255.40   $255.40   $255.40  
  7 purchase totals = $964.94       $1,046.0157   $1,046.02   $1,046.00   $1,046.10