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 $114.94   9.480%   $125.8363   $125.84   $125.85   $125.80  
  Purchase #2 $118.91   3.413%   $122.9684   $122.97   $122.95   $123.00  
  Purchase #3 $201.27   6.543%   $214.4391   $214.44   $214.45   $214.40  
  Purchase #4 $35.69   9.825%   $39.1965   $39.20   $39.20   $39.20  
  Purchase #5 $222.78   4.707%   $233.2663   $233.27   $233.25   $233.30  
  Purchase #6 $55.81   8.762%   $60.7001   $60.70   $60.70   $60.70  
  Purchase #7 $180.30   9.612%   $197.6304   $197.63   $197.65   $197.60  
  7 purchase totals = $929.70       $994.0371   $994.05   $994.05   $994.00