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 $61.54   13.624%   $69.9242   $69.92   $69.90   $69.90  
  Purchase #2 $56.25   9.303%   $61.4829   $61.48   $61.50   $61.50  
  Purchase #3 $8.63   5.707%   $9.1225   $9.12   $9.10   $9.10  
  Purchase #4 $22.82   12.132%   $25.5885   $25.59   $25.60   $25.60  
  Purchase #5 $198.67   4.760%   $208.1267   $208.13   $208.15   $208.10  
  Purchase #6 $224.44   10.816%   $248.7154   $248.72   $248.70   $248.70  
  Purchase #7 $122.62   9.540%   $134.3179   $134.32   $134.30   $134.30  
  7 purchase totals = $694.97       $757.2781   $757.28   $757.25   $757.20