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 $84.63   3.108%   $87.2603   $87.26   $87.25   $87.30  
  Purchase #2 $219.86   11.390%   $244.9021   $244.90   $244.90   $244.90  
  Purchase #3 $171.66   3.431%   $177.5497   $177.55   $177.55   $177.50  
  Purchase #4 $146.99   5.714%   $155.389   $155.39   $155.40   $155.40  
  Purchase #5 $21.61   12.430%   $24.2961   $24.30   $24.30   $24.30  
  Purchase #6 $207.32   3.651%   $214.8893   $214.89   $214.90   $214.90  
  Purchase #7 $207.39   4.255%   $216.2144   $216.21   $216.20   $216.20  
  7 purchase totals = $1,059.46       $1,120.5009   $1,120.50   $1,120.50   $1,120.50