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 $181.77   8.690%   $197.5658   $197.57   $197.55   $197.60  
  Purchase #2 $207.78   3.392%   $214.8279   $214.83   $214.85   $214.80  
  Purchase #3 $160.78   3.413%   $166.2674   $166.27   $166.25   $166.30  
  Purchase #4 $107.66   13.220%   $121.8927   $121.89   $121.90   $121.90  
  Purchase #5 $126.60   3.706%   $131.2918   $131.29   $131.30   $131.30  
  Purchase #6 $246.26   4.422%   $257.1496   $257.15   $257.15   $257.10  
  Purchase #7 $70.70   13.802%   $80.458   $80.46   $80.45   $80.50  
  7 purchase totals = $1,101.55       $1,169.4532   $1,169.46   $1,169.45   $1,169.50