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 $108.98   4.795%   $114.2056   $114.21   $114.20   $114.20  
  Purchase #2 $227.89   8.272%   $246.7411   $246.74   $246.75   $246.70  
  Purchase #3 $44.42   7.792%   $47.8812   $47.88   $47.90   $47.90  
  Purchase #4 $138.81   12.605%   $156.307   $156.31   $156.30   $156.30  
  Purchase #5 $217.59   10.811%   $241.1137   $241.11   $241.10   $241.10  
  Purchase #6 $13.25   7.197%   $14.2036   $14.20   $14.20   $14.20  
  Purchase #7 $201.41   11.807%   $225.1905   $225.19   $225.20   $225.20  
  7 purchase totals = $952.35       $1,045.6427   $1,045.64   $1,045.65   $1,045.60