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 $41.46   12.333%   $46.5733   $46.57   $46.55   $46.60  
  Purchase #2 $228.55   3.120%   $235.6808   $235.68   $235.70   $235.70  
  Purchase #3 $164.87   6.186%   $175.0689   $175.07   $175.05   $175.10  
  Purchase #4 $126.87   3.401%   $131.1848   $131.18   $131.20   $131.20  
  Purchase #5 $38.65   4.574%   $40.4179   $40.42   $40.40   $40.40  
  Purchase #6 $175.79   12.785%   $198.2648   $198.26   $198.25   $198.30  
  Purchase #7 $170.89   9.424%   $186.9947   $186.99   $187.00   $187.00  
  7 purchase totals = $947.08       $1,014.1852   $1,014.17   $1,014.15   $1,014.30