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 $220.46   5.347%   $232.248   $232.25   $232.25   $232.20  
  Purchase #2 $104.80   9.608%   $114.8692   $114.87   $114.85   $114.90  
  Purchase #3 $66.36   11.441%   $73.9522   $73.95   $73.95   $74.00  
  Purchase #4 $205.56   3.119%   $211.9714   $211.97   $211.95   $212.00  
  Purchase #5 $82.54   11.685%   $92.1848   $92.18   $92.20   $92.20  
  Purchase #6 $61.27   12.302%   $68.8074   $68.81   $68.80   $68.80  
  Purchase #7 $196.26   6.847%   $209.6979   $209.70   $209.70   $209.70  
  7 purchase totals = $937.25       $1,003.7309   $1,003.73   $1,003.70   $1,003.80