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 $110.48   3.216%   $114.033   $114.03   $114.05   $114.00  
  Purchase #2 $10.72   9.496%   $11.738   $11.74   $11.75   $11.70  
  Purchase #3 $73.67   5.117%   $77.4397   $77.44   $77.45   $77.40  
  Purchase #4 $93.42   5.224%   $98.3003   $98.30   $98.30   $98.30  
  Purchase #5 $13.82   4.112%   $14.3883   $14.39   $14.40   $14.40  
  Purchase #6 $218.31   7.676%   $235.0675   $235.07   $235.05   $235.10  
  Purchase #7 $174.90   9.479%   $191.4788   $191.48   $191.50   $191.50  
  7 purchase totals = $695.32       $742.4456   $742.45   $742.50   $742.40