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 $86.65   10.211%   $95.4978   $95.50   $95.50   $95.50  
  Purchase #2 $78.32   8.550%   $85.0164   $85.02   $85.00   $85.00  
  Purchase #3 $218.65   6.300%   $232.425   $232.43   $232.45   $232.40  
  Purchase #4 $95.50   12.340%   $107.2847   $107.28   $107.30   $107.30  
  Purchase #5 $222.40   8.550%   $241.4152   $241.42   $241.40   $241.40  
  Purchase #6 $13.70   3.197%   $14.138   $14.14   $14.15   $14.10  
  Purchase #7 $19.84   4.179%   $20.6691   $20.67   $20.65   $20.70  
  7 purchase totals = $735.06       $796.4462   $796.46   $796.45   $796.40