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 $89.90   7.681%   $96.8052   $96.81   $96.80   $96.80  
  Purchase #2 $58.47   5.873%   $61.9039   $61.90   $61.90   $61.90  
  Purchase #3 $35.52   11.360%   $39.5551   $39.56   $39.55   $39.60  
  Purchase #4 $82.47   13.659%   $93.7346   $93.73   $93.75   $93.70  
  Purchase #5 $170.94   6.751%   $182.4802   $182.48   $182.50   $182.50  
  Purchase #6 $74.55   11.375%   $83.0301   $83.03   $83.05   $83.00  
  Purchase #7 $163.39   7.402%   $175.4841   $175.48   $175.50   $175.50  
  7 purchase totals = $675.24       $732.9932   $732.99   $733.05   $733.00