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 $62.54   7.193%   $67.0385   $67.04   $67.05   $67.00  
  Purchase #2 $204.65   10.341%   $225.8129   $225.81   $225.80   $225.80  
  Purchase #3 $6.25   4.326%   $6.5204   $6.52   $6.50   $6.50  
  Purchase #4 $186.88   9.801%   $205.1961   $205.20   $205.20   $205.20  
  Purchase #5 $201.30   4.606%   $210.5719   $210.57   $210.55   $210.60  
  Purchase #6 $38.44   3.716%   $39.8684   $39.87   $39.85   $39.90  
  Purchase #7 $5.65   7.840%   $6.093   $6.09   $6.10   $6.10  
  7 purchase totals = $705.71       $761.1012   $761.10   $761.05   $761.10