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 $87.34   9.644%   $95.7631   $95.76   $95.75   $95.80  
  Purchase #2 $216.78   11.492%   $241.6924   $241.69   $241.70   $241.70  
  Purchase #3 $27.66   12.609%   $31.1476   $31.15   $31.15   $31.10  
  Purchase #4 $58.66   9.413%   $64.1817   $64.18   $64.20   $64.20  
  Purchase #5 $229.70   10.833%   $254.5834   $254.58   $254.60   $254.60  
  Purchase #6 $35.76   6.409%   $38.0519   $38.05   $38.05   $38.10  
  Purchase #7 $217.65   9.681%   $238.7207   $238.72   $238.70   $238.70  
  7 purchase totals = $873.55       $964.1408   $964.13   $964.15   $964.20