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 $86.61   8.830%   $94.2577   $94.26   $94.25   $94.30  
  Purchase #2 $112.27   5.488%   $118.4314   $118.43   $118.45   $118.40  
  Purchase #3 $250.78   9.433%   $274.4361   $274.44   $274.45   $274.40  
  Purchase #4 $122.99   12.449%   $138.301   $138.30   $138.30   $138.30  
  Purchase #5 $61.81   5.225%   $65.0396   $65.04   $65.05   $65.00  
  Purchase #6 $231.63   4.389%   $241.7962   $241.80   $241.80   $241.80  
  Purchase #7 $198.73   11.732%   $222.045   $222.05   $222.05   $222.00  
  7 purchase totals = $1,064.82       $1,154.3070   $1,154.32   $1,154.35   $1,154.20