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 $74.81   4.208%   $77.958   $77.96   $77.95   $78.00  
  Purchase #2 $233.54   12.480%   $262.6858   $262.69   $262.70   $262.70  
  Purchase #3 $24.84   6.690%   $26.5018   $26.50   $26.50   $26.50  
  Purchase #4 $229.66   7.594%   $247.1004   $247.10   $247.10   $247.10  
  Purchase #5 $174.38   12.202%   $195.6578   $195.66   $195.65   $195.70  
  Purchase #6 $14.67   7.821%   $15.8173   $15.82   $15.80   $15.80  
  Purchase #7 $118.77   5.632%   $125.4591   $125.46   $125.45   $125.50  
  7 purchase totals = $870.67       $951.1802   $951.19   $951.15   $951.30