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 $42.83   4.366%   $44.7   $44.70   $44.70   $44.70  
  Purchase #2 $215.35   8.126%   $232.8493   $232.85   $232.85   $232.80  
  Purchase #3 $60.85   10.303%   $67.1194   $67.12   $67.10   $67.10  
  Purchase #4 $206.98   10.732%   $229.1931   $229.19   $229.20   $229.20  
  Purchase #5 $185.92   9.774%   $204.0918   $204.09   $204.10   $204.10  
  Purchase #6 $103.99   13.376%   $117.8997   $117.90   $117.90   $117.90  
  Purchase #7 $146.98   11.373%   $163.696   $163.70   $163.70   $163.70  
  7 purchase totals = $962.90       $1,059.5493   $1,059.55   $1,059.55   $1,059.50