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 $222.59   6.754%   $237.6237   $237.62   $237.60   $237.60  
  Purchase #2 $82.74   4.319%   $86.3135   $86.31   $86.30   $86.30  
  Purchase #3 $217.53   4.604%   $227.5451   $227.55   $227.55   $227.50  
  Purchase #4 $65.78   3.274%   $67.9336   $67.93   $67.95   $67.90  
  Purchase #5 $98.38   4.325%   $102.6349   $102.63   $102.65   $102.60  
  Purchase #6 $248.60   4.743%   $260.3911   $260.39   $260.40   $260.40  
  Purchase #7 $173.34   11.490%   $193.2568   $193.26   $193.25   $193.30  
  7 purchase totals = $1,108.96       $1,175.6987   $1,175.69   $1,175.70   $1,175.60