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 $88.76   5.771%   $93.8823   $93.88   $93.90   $93.90  
  Purchase #2 $114.67   5.360%   $120.8163   $120.82   $120.80   $120.80  
  Purchase #3 $88.74   5.232%   $93.3829   $93.38   $93.40   $93.40  
  Purchase #4 $229.35   8.450%   $248.7301   $248.73   $248.75   $248.70  
  Purchase #5 $147.83   10.709%   $163.6611   $163.66   $163.65   $163.70  
  Purchase #6 $217.46   5.104%   $228.5592   $228.56   $228.55   $228.60  
  Purchase #7 $193.86   3.788%   $201.2034   $201.20   $201.20   $201.20  
  7 purchase totals = $1,080.67       $1,150.2353   $1,150.23   $1,150.25   $1,150.30