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 $95.82   6.723%   $102.262   $102.26   $102.25   $102.30  
  Purchase #2 $200.47   6.569%   $213.6389   $213.64   $213.65   $213.60  
  Purchase #3 $12.80   11.435%   $14.2637   $14.26   $14.25   $14.30  
  Purchase #4 $240.87   3.574%   $249.4787   $249.48   $249.50   $249.50  
  Purchase #5 $117.58   5.554%   $124.1104   $124.11   $124.10   $124.10  
  Purchase #6 $206.57   8.654%   $224.4466   $224.45   $224.45   $224.40  
  Purchase #7 $138.63   12.190%   $155.529   $155.53   $155.55   $155.50  
  7 purchase totals = $1,012.74       $1,083.7293   $1,083.73   $1,083.75   $1,083.70