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 $61.92   10.765%   $68.5857   $68.59   $68.60   $68.60  
  Purchase #2 $202.56   7.484%   $217.7196   $217.72   $217.70   $217.70  
  Purchase #3 $152.79   12.774%   $172.3074   $172.31   $172.30   $172.30  
  Purchase #4 $211.66   11.154%   $235.2686   $235.27   $235.25   $235.30  
  Purchase #5 $214.86   10.203%   $236.7822   $236.78   $236.80   $236.80  
  Purchase #6 $113.26   11.149%   $125.8874   $125.89   $125.90   $125.90  
  Purchase #7 $171.85   10.783%   $190.3806   $190.38   $190.40   $190.40  
  7 purchase totals = $1,128.90       $1,246.9315   $1,246.94   $1,246.95   $1,247.00