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 $58.55   6.789%   $62.525   $62.53   $62.55   $62.50  
  Purchase #2 $215.66   5.603%   $227.7434   $227.74   $227.75   $227.70  
  Purchase #3 $42.90   6.490%   $45.6842   $45.68   $45.70   $45.70  
  Purchase #4 $95.66   8.827%   $104.1039   $104.10   $104.10   $104.10  
  Purchase #5 $67.53   4.129%   $70.3183   $70.32   $70.30   $70.30  
  Purchase #6 $218.57   4.706%   $228.8559   $228.86   $228.85   $228.90  
  Purchase #7 $206.30   11.730%   $230.499   $230.50   $230.50   $230.50  
  7 purchase totals = $905.17       $969.7297   $969.73   $969.75   $969.70