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 $240.88   5.333%   $253.7261   $253.73   $253.75   $253.70  
  Purchase #2 $44.66   4.528%   $46.6822   $46.68   $46.70   $46.70  
  Purchase #3 $166.82   4.846%   $174.9041   $174.90   $174.90   $174.90  
  Purchase #4 $231.31   4.358%   $241.3905   $241.39   $241.40   $241.40  
  Purchase #5 $154.27   4.147%   $160.6676   $160.67   $160.65   $160.70  
  Purchase #6 $52.86   9.832%   $58.0572   $58.06   $58.05   $58.10  
  Purchase #7 $159.74   4.204%   $166.4555   $166.46   $166.45   $166.50  
  7 purchase totals = $1,050.54       $1,101.8832   $1,101.89   $1,101.90   $1,102.00