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 $65.87   12.271%   $73.9529   $73.95   $73.95   $74.00  
  Purchase #2 $112.51   12.564%   $126.6458   $126.65   $126.65   $126.60  
  Purchase #3 $28.26   7.478%   $30.3733   $30.37   $30.35   $30.40  
  Purchase #4 $155.69   3.239%   $160.7328   $160.73   $160.75   $160.70  
  Purchase #5 $212.42   5.396%   $223.8822   $223.88   $223.90   $223.90  
  Purchase #6 $214.77   4.149%   $223.6808   $223.68   $223.70   $223.70  
  Purchase #7 $201.87   9.345%   $220.7348   $220.73   $220.75   $220.70  
  7 purchase totals = $991.39       $1,060.0026   $1,059.99   $1,060.05   $1,060.00