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 $87.44   8.304%   $94.701   $94.70   $94.70   $94.70  
  Purchase #2 $199.44   3.608%   $206.6358   $206.64   $206.65   $206.60  
  Purchase #3 $231.32   12.215%   $259.5757   $259.58   $259.60   $259.60  
  Purchase #4 $28.73   3.179%   $29.6433   $29.64   $29.65   $29.60  
  Purchase #5 $226.86   5.595%   $239.5528   $239.55   $239.55   $239.60  
  Purchase #6 $68.57   5.867%   $72.593   $72.59   $72.60   $72.60  
  Purchase #7 $245.26   6.179%   $260.4146   $260.41   $260.40   $260.40  
  7 purchase totals = $1,087.62       $1,163.1162   $1,163.11   $1,163.15   $1,163.10