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 $116.86   5.445%   $123.223   $123.22   $123.20   $123.20  
  Purchase #2 $120.79   5.715%   $127.6931   $127.69   $127.70   $127.70  
  Purchase #3 $193.76   5.652%   $204.7113   $204.71   $204.70   $204.70  
  Purchase #4 $216.70   3.794%   $224.9216   $224.92   $224.90   $224.90  
  Purchase #5 $182.54   5.531%   $192.6363   $192.64   $192.65   $192.60  
  Purchase #6 $199.96   5.285%   $210.5279   $210.53   $210.55   $210.50  
  Purchase #7 $79.56   10.576%   $87.9743   $87.97   $87.95   $88.00  
  7 purchase totals = $1,110.17       $1,171.6875   $1,171.68   $1,171.65   $1,171.60