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 $71.66   5.660%   $75.716   $75.72   $75.70   $75.70  
  Purchase #2 $110.29   6.359%   $117.3033   $117.30   $117.30   $117.30  
  Purchase #3 $109.88   10.577%   $121.502   $121.50   $121.50   $121.50  
  Purchase #4 $177.64   11.628%   $198.296   $198.30   $198.30   $198.30  
  Purchase #5 $107.59   5.856%   $113.8905   $113.89   $113.90   $113.90  
  Purchase #6 $57.57   5.466%   $60.7168   $60.72   $60.70   $60.70  
  Purchase #7 $80.27   6.873%   $85.787   $85.79   $85.80   $85.80  
  7 purchase totals = $714.90       $773.2116   $773.22   $773.20   $773.20