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 $89.74   5.133%   $94.3464   $94.35   $94.35   $94.30  
  Purchase #2 $197.38   8.179%   $213.5237   $213.52   $213.50   $213.50  
  Purchase #3 $8.88   13.299%   $10.061   $10.06   $10.05   $10.10  
  Purchase #4 $60.51   11.293%   $67.3434   $67.34   $67.35   $67.30  
  Purchase #5 $177.79   10.783%   $196.9611   $196.96   $196.95   $197.00  
  Purchase #6 $26.95   13.249%   $30.5206   $30.52   $30.50   $30.50  
  Purchase #7 $134.93   3.569%   $139.7457   $139.75   $139.75   $139.70  
  7 purchase totals = $696.18       $752.5019   $752.50   $752.45   $752.40