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 $43.92   6.624%   $46.8293   $46.83   $46.85   $46.80  
  Purchase #2 $20.26   12.502%   $22.7929   $22.79   $22.80   $22.80  
  Purchase #3 $71.99   6.762%   $76.858   $76.86   $76.85   $76.90  
  Purchase #4 $228.65   3.145%   $235.841   $235.84   $235.85   $235.80  
  Purchase #5 $237.54   3.189%   $245.1152   $245.12   $245.10   $245.10  
  Purchase #6 $116.28   9.820%   $127.6987   $127.70   $127.70   $127.70  
  Purchase #7 $236.38   9.772%   $259.4791   $259.48   $259.50   $259.50  
  7 purchase totals = $955.02       $1,014.6142   $1,014.62   $1,014.65   $1,014.60