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 $191.64   6.368%   $203.8436   $203.84   $203.85   $203.80  
  Purchase #2 $30.69   8.296%   $33.236   $33.24   $33.25   $33.20  
  Purchase #3 $193.39   13.174%   $218.8672   $218.87   $218.85   $218.90  
  Purchase #4 $180.33   13.826%   $205.2624   $205.26   $205.25   $205.30  
  Purchase #5 $149.63   9.857%   $164.379   $164.38   $164.40   $164.40  
  Purchase #6 $244.55   7.442%   $262.7494   $262.75   $262.75   $262.70  
  Purchase #7 $56.29   13.791%   $64.053   $64.05   $64.05   $64.10  
  7 purchase totals = $1,046.52       $1,152.3906   $1,152.39   $1,152.40   $1,152.40