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 $101.73   12.703%   $114.6528   $114.65   $114.65   $114.70  
  Purchase #2 $153.28   8.854%   $166.8514   $166.85   $166.85   $166.90  
  Purchase #3 $136.94   12.473%   $154.0205   $154.02   $154.00   $154.00  
  Purchase #4 $126.61   5.479%   $133.547   $133.55   $133.55   $133.50  
  Purchase #5 $207.37   12.341%   $232.9615   $232.96   $232.95   $233.00  
  Purchase #6 $234.92   7.561%   $252.6823   $252.68   $252.70   $252.70  
  Purchase #7 $94.25   8.184%   $101.9634   $101.96   $101.95   $102.00  
  7 purchase totals = $1,055.10       $1,156.6789   $1,156.67   $1,156.65   $1,156.80