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 $61.63   8.697%   $66.99   $66.99   $67.00   $67.00  
  Purchase #2 $235.64   13.446%   $267.3242   $267.32   $267.30   $267.30  
  Purchase #3 $53.69   11.366%   $59.7924   $59.79   $59.80   $59.80  
  Purchase #4 $141.63   4.505%   $148.0104   $148.01   $148.00   $148.00  
  Purchase #5 $123.38   4.344%   $128.7396   $128.74   $128.75   $128.70  
  Purchase #6 $246.35   6.370%   $262.0425   $262.04   $262.05   $262.00  
  Purchase #7 $197.26   5.801%   $208.7031   $208.70   $208.70   $208.70  
  7 purchase totals = $1,059.58       $1,141.6022   $1,141.59   $1,141.60   $1,141.50