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 $64.36   5.666%   $68.0066   $68.01   $68.00   $68.00  
  Purchase #2 $237.67   3.403%   $245.7579   $245.76   $245.75   $245.80  
  Purchase #3 $175.27   4.815%   $183.7093   $183.71   $183.70   $183.70  
  Purchase #4 $237.63   6.116%   $252.1635   $252.16   $252.15   $252.20  
  Purchase #5 $167.33   12.583%   $188.3851   $188.39   $188.40   $188.40  
  Purchase #6 $166.35   12.586%   $187.2868   $187.29   $187.30   $187.30  
  Purchase #7 $55.58   3.172%   $57.343   $57.34   $57.35   $57.30  
  7 purchase totals = $1,104.19       $1,182.6522   $1,182.66   $1,182.65   $1,182.70