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 $42.94   8.840%   $46.7359   $46.74   $46.75   $46.70  
  Purchase #2 $205.57   11.240%   $228.6761   $228.68   $228.70   $228.70  
  Purchase #3 $235.56   12.104%   $264.0722   $264.07   $264.05   $264.10  
  Purchase #4 $207.35   11.685%   $231.5788   $231.58   $231.60   $231.60  
  Purchase #5 $135.84   6.815%   $145.0975   $145.10   $145.10   $145.10  
  Purchase #6 $31.31   10.534%   $34.6082   $34.61   $34.60   $34.60  
  Purchase #7 $239.57   5.422%   $252.5595   $252.56   $252.55   $252.60  
  7 purchase totals = $1,098.14       $1,203.3282   $1,203.34   $1,203.35   $1,203.40