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 $46.65   11.405%   $51.9704   $51.97   $51.95   $52.00  
  Purchase #2 $156.73   10.221%   $172.7494   $172.75   $172.75   $172.70  
  Purchase #3 $159.75   3.446%   $165.255   $165.26   $165.25   $165.30  
  Purchase #4 $148.62   9.637%   $162.9425   $162.94   $162.95   $162.90  
  Purchase #5 $129.83   6.460%   $138.217   $138.22   $138.20   $138.20  
  Purchase #6 $60.42   8.724%   $65.691   $65.69   $65.70   $65.70  
  Purchase #7 $5.51   6.803%   $5.8848   $5.88   $5.90   $5.90  
  7 purchase totals = $707.51       $762.7101   $762.71   $762.70   $762.70