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 $194.88   5.585%   $205.764   $205.76   $205.75   $205.80  
  Purchase #2 $14.97   8.372%   $16.2233   $16.22   $16.20   $16.20  
  Purchase #3 $167.33   11.306%   $186.2483   $186.25   $186.25   $186.20  
  Purchase #4 $86.74   7.621%   $93.3505   $93.35   $93.35   $93.40  
  Purchase #5 $114.25   3.222%   $117.9311   $117.93   $117.95   $117.90  
  Purchase #6 $66.30   5.290%   $69.8073   $69.81   $69.80   $69.80  
  Purchase #7 $169.54   5.822%   $179.4106   $179.41   $179.40   $179.40  
  7 purchase totals = $814.01       $868.7351   $868.73   $868.70   $868.70