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 $85.60   11.258%   $95.2368   $95.24   $95.25   $95.20  
  Purchase #2 $10.70   3.247%   $11.0474   $11.05   $11.05   $11.00  
  Purchase #3 $144.33   9.383%   $157.8725   $157.87   $157.85   $157.90  
  Purchase #4 $156.25   6.399%   $166.2484   $166.25   $166.25   $166.20  
  Purchase #5 $182.73   12.609%   $205.7704   $205.77   $205.75   $205.80  
  Purchase #6 $52.29   5.377%   $55.1016   $55.10   $55.10   $55.10  
  Purchase #7 $228.72   13.453%   $259.4897   $259.49   $259.50   $259.50  
  7 purchase totals = $860.62       $950.7668   $950.77   $950.75   $950.70