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 $195.69   12.225%   $219.6131   $219.61   $219.60   $219.60  
  Purchase #2 $98.41   9.459%   $107.7186   $107.72   $107.70   $107.70  
  Purchase #3 $185.95   5.823%   $196.7779   $196.78   $196.80   $196.80  
  Purchase #4 $162.77   11.513%   $181.5097   $181.51   $181.50   $181.50  
  Purchase #5 $23.57   4.599%   $24.654   $24.65   $24.65   $24.70  
  Purchase #6 $227.86   11.373%   $253.7745   $253.77   $253.75   $253.80  
  Purchase #7 $139.66   5.102%   $146.7855   $146.79   $146.80   $146.80  
  7 purchase totals = $1,033.91       $1,130.8333   $1,130.83   $1,130.80   $1,130.90