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 $92.59   3.351%   $95.6927   $95.69   $95.70   $95.70  
  Purchase #2 $78.69   9.544%   $86.2002   $86.20   $86.20   $86.20  
  Purchase #3 $119.36   10.438%   $131.8188   $131.82   $131.80   $131.80  
  Purchase #4 $24.57   11.144%   $27.3081   $27.31   $27.30   $27.30  
  Purchase #5 $99.99   4.393%   $104.3826   $104.38   $104.40   $104.40  
  Purchase #6 $107.25   13.614%   $121.851   $121.85   $121.85   $121.90  
  Purchase #7 $46.86   5.125%   $49.2616   $49.26   $49.25   $49.30  
  7 purchase totals = $569.31       $616.5150   $616.51   $616.50   $616.60