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 $191.25   7.676%   $205.9304   $205.93   $205.95   $205.90  
  Purchase #2 $140.44   8.729%   $152.699   $152.70   $152.70   $152.70  
  Purchase #3 $62.37   13.162%   $70.5791   $70.58   $70.60   $70.60  
  Purchase #4 $207.54   3.496%   $214.7956   $214.80   $214.80   $214.80  
  Purchase #5 $69.38   7.361%   $74.4871   $74.49   $74.50   $74.50  
  Purchase #6 $64.84   7.125%   $69.4599   $69.46   $69.45   $69.50  
  Purchase #7 $125.47   9.321%   $137.1651   $137.17   $137.15   $137.20  
  7 purchase totals = $861.29       $925.1162   $925.13   $925.15   $925.20