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 $69.26   6.238%   $73.5804   $73.58   $73.60   $73.60  
  Purchase #2 $162.58   11.147%   $180.7028   $180.70   $180.70   $180.70  
  Purchase #3 $52.39   6.342%   $55.7126   $55.71   $55.70   $55.70  
  Purchase #4 $203.91   10.308%   $224.929   $224.93   $224.95   $224.90  
  Purchase #5 $58.45   8.127%   $63.2002   $63.20   $63.20   $63.20  
  Purchase #6 $35.56   13.445%   $40.341   $40.34   $40.35   $40.30  
  Purchase #7 $84.80   4.439%   $88.5643   $88.56   $88.55   $88.60  
  7 purchase totals = $666.95       $727.0303   $727.02   $727.05   $727.00