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 $24.86   3.230%   $25.663   $25.66   $25.65   $25.70  
  Purchase #2 $116.47   12.844%   $131.4294   $131.43   $131.45   $131.40  
  Purchase #3 $221.81   11.139%   $246.5174   $246.52   $246.50   $246.50  
  Purchase #4 $106.82   5.433%   $112.6235   $112.62   $112.60   $112.60  
  Purchase #5 $146.46   4.411%   $152.9204   $152.92   $152.90   $152.90  
  Purchase #6 $9.85   4.297%   $10.2733   $10.27   $10.25   $10.30  
  Purchase #7 $75.43   8.378%   $81.7495   $81.75   $81.75   $81.70  
  7 purchase totals = $701.70       $761.1765   $761.17   $761.10   $761.10