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 $219.80   5.373%   $231.6099   $231.61   $231.60   $231.60  
  Purchase #2 $217.54   10.182%   $239.6899   $239.69   $239.70   $239.70  
  Purchase #3 $200.56   5.624%   $211.8395   $211.84   $211.85   $211.80  
  Purchase #4 $77.79   6.872%   $83.1357   $83.14   $83.15   $83.10  
  Purchase #5 $206.31   5.681%   $218.0305   $218.03   $218.05   $218.00  
  Purchase #6 $210.62   6.301%   $223.8912   $223.89   $223.90   $223.90  
  Purchase #7 $130.35   6.689%   $139.0691   $139.07   $139.05   $139.10  
  7 purchase totals = $1,262.97       $1,347.2658   $1,347.27   $1,347.30   $1,347.20