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 $204.40   9.592%   $224.006   $224.01   $224.00   $224.00  
  Purchase #2 $88.91   11.186%   $98.8555   $98.86   $98.85   $98.90  
  Purchase #3 $92.82   6.420%   $98.779   $98.78   $98.80   $98.80  
  Purchase #4 $242.91   6.402%   $258.4611   $258.46   $258.45   $258.50  
  Purchase #5 $61.71   6.792%   $65.9013   $65.90   $65.90   $65.90  
  Purchase #6 $201.29   5.770%   $212.9044   $212.90   $212.90   $212.90  
  Purchase #7 $110.66   3.659%   $114.709   $114.71   $114.70   $114.70  
  7 purchase totals = $1,002.70       $1,073.6163   $1,073.62   $1,073.60   $1,073.70