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 $33.47   3.661%   $34.6953   $34.70   $34.70   $34.70  
  Purchase #2 $158.81   3.290%   $164.0348   $164.03   $164.05   $164.00  
  Purchase #3 $64.45   5.840%   $68.2139   $68.21   $68.20   $68.20  
  Purchase #4 $232.42   3.684%   $240.9824   $240.98   $241.00   $241.00  
  Purchase #5 $234.37   12.751%   $264.2545   $264.25   $264.25   $264.30  
  Purchase #6 $180.80   9.136%   $197.3179   $197.32   $197.30   $197.30  
  Purchase #7 $39.72   12.688%   $44.7597   $44.76   $44.75   $44.80  
  7 purchase totals = $944.04       $1,014.2585   $1,014.25   $1,014.25   $1,014.30