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 $69.75   9.402%   $76.3079   $76.31   $76.30   $76.30  
  Purchase #2 $63.62   11.861%   $71.166   $71.17   $71.15   $71.20  
  Purchase #3 $222.94   10.134%   $245.5327   $245.53   $245.55   $245.50  
  Purchase #4 $51.37   13.463%   $58.2859   $58.29   $58.30   $58.30  
  Purchase #5 $214.67   4.659%   $224.6715   $224.67   $224.65   $224.70  
  Purchase #6 $207.93   10.131%   $228.9954   $229.00   $229.00   $229.00  
  Purchase #7 $117.59   11.642%   $131.2798   $131.28   $131.30   $131.30  
  7 purchase totals = $947.87       $1,036.2392   $1,036.25   $1,036.25   $1,036.30