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 $216.82   7.228%   $232.4917   $232.49   $232.50   $232.50  
  Purchase #2 $166.43   11.234%   $185.1267   $185.13   $185.15   $185.10  
  Purchase #3 $226.77   7.187%   $243.068   $243.07   $243.05   $243.10  
  Purchase #4 $38.50   7.457%   $41.3709   $41.37   $41.35   $41.40  
  Purchase #5 $153.49   4.695%   $160.6964   $160.70   $160.70   $160.70  
  Purchase #6 $174.83   13.709%   $198.7974   $198.80   $198.80   $198.80  
  Purchase #7 $33.47   5.331%   $35.2543   $35.25   $35.25   $35.30  
  7 purchase totals = $1,010.31       $1,096.8054   $1,096.81   $1,096.80   $1,096.90