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 $71.95   5.574%   $75.9605   $75.96   $75.95   $76.00  
  Purchase #2 $144.49   11.294%   $160.8087   $160.81   $160.80   $160.80  
  Purchase #3 $88.46   10.728%   $97.95   $97.95   $97.95   $98.00  
  Purchase #4 $49.80   3.506%   $51.546   $51.55   $51.55   $51.50  
  Purchase #5 $127.66   4.863%   $133.8681   $133.87   $133.85   $133.90  
  Purchase #6 $169.49   7.792%   $182.6967   $182.70   $182.70   $182.70  
  Purchase #7 $40.35   6.166%   $42.838   $42.84   $42.85   $42.80  
  7 purchase totals = $692.20       $745.6680   $745.68   $745.65   $745.70