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 $110.78   13.470%   $125.7021   $125.70   $125.70   $125.70  
  Purchase #2 $151.56   7.781%   $163.3529   $163.35   $163.35   $163.40  
  Purchase #3 $7.96   6.183%   $8.4522   $8.45   $8.45   $8.50  
  Purchase #4 $191.73   7.623%   $206.3456   $206.35   $206.35   $206.30  
  Purchase #5 $96.58   7.824%   $104.1364   $104.14   $104.15   $104.10  
  Purchase #6 $57.59   5.833%   $60.9492   $60.95   $60.95   $60.90  
  Purchase #7 $82.57   12.109%   $92.5684   $92.57   $92.55   $92.60  
  7 purchase totals = $698.77       $761.5068   $761.51   $761.50   $761.50