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 $68.49   8.692%   $74.4432   $74.44   $74.45   $74.40  
  Purchase #2 $104.87   8.659%   $113.9507   $113.95   $113.95   $114.00  
  Purchase #3 $187.32   7.436%   $201.2491   $201.25   $201.25   $201.20  
  Purchase #4 $81.31   8.199%   $87.9766   $87.98   $88.00   $88.00  
  Purchase #5 $203.98   13.196%   $230.8972   $230.90   $230.90   $230.90  
  Purchase #6 $215.72   6.419%   $229.5671   $229.57   $229.55   $229.60  
  Purchase #7 $212.28   10.141%   $233.8073   $233.81   $233.80   $233.80  
  7 purchase totals = $1,073.97       $1,171.8912   $1,171.90   $1,171.90   $1,171.90