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 $241.76   11.274%   $269.016   $269.02   $269.00   $269.00  
  Purchase #2 $67.34   7.772%   $72.5737   $72.57   $72.55   $72.60  
  Purchase #3 $163.36   12.218%   $183.3193   $183.32   $183.30   $183.30  
  Purchase #4 $45.59   13.347%   $51.6749   $51.67   $51.65   $51.70  
  Purchase #5 $35.95   12.826%   $40.5609   $40.56   $40.55   $40.60  
  Purchase #6 $197.53   8.381%   $214.085   $214.09   $214.10   $214.10  
  Purchase #7 $199.44   6.641%   $212.6848   $212.68   $212.70   $212.70  
  7 purchase totals = $950.97       $1,043.9146   $1,043.91   $1,043.85   $1,044.00