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 $214.52   5.262%   $225.808   $225.81   $225.80   $225.80  
  Purchase #2 $210.38   6.416%   $223.878   $223.88   $223.90   $223.90  
  Purchase #3 $149.67   3.106%   $154.3188   $154.32   $154.30   $154.30  
  Purchase #4 $60.26   10.224%   $66.421   $66.42   $66.40   $66.40  
  Purchase #5 $23.57   13.667%   $26.7913   $26.79   $26.80   $26.80  
  Purchase #6 $231.97   8.143%   $250.8593   $250.86   $250.85   $250.90  
  Purchase #7 $232.90   7.675%   $250.7751   $250.78   $250.80   $250.80  
  7 purchase totals = $1,123.27       $1,198.8515   $1,198.86   $1,198.85   $1,198.90