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 $193.94   5.831%   $205.2486   $205.25   $205.25   $205.20  
  Purchase #2 $100.97   8.274%   $109.3243   $109.32   $109.30   $109.30  
  Purchase #3 $126.82   7.299%   $136.0766   $136.08   $136.10   $136.10  
  Purchase #4 $157.26   11.195%   $174.8653   $174.87   $174.85   $174.90  
  Purchase #5 $122.54   5.271%   $128.9991   $129.00   $129.00   $129.00  
  Purchase #6 $110.29   4.267%   $114.9961   $115.00   $115.00   $115.00  
  Purchase #7 $154.58   5.322%   $162.8067   $162.81   $162.80   $162.80  
  7 purchase totals = $966.40       $1,032.3167   $1,032.33   $1,032.30   $1,032.30