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 $63.56   8.653%   $69.0598   $69.06   $69.05   $69.10  
  Purchase #2 $239.43   13.614%   $272.026   $272.03   $272.05   $272.00  
  Purchase #3 $175.82   11.192%   $195.4978   $195.50   $195.50   $195.50  
  Purchase #4 $37.27   12.434%   $41.9042   $41.90   $41.90   $41.90  
  Purchase #5 $197.45   5.848%   $208.9969   $209.00   $209.00   $209.00  
  Purchase #6 $76.37   6.834%   $81.5891   $81.59   $81.60   $81.60  
  Purchase #7 $191.89   7.156%   $205.6216   $205.62   $205.60   $205.60  
  7 purchase totals = $981.79       $1,074.6954   $1,074.70   $1,074.70   $1,074.70