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 $212.41   10.782%   $235.312   $235.31   $235.30   $235.30  
  Purchase #2 $243.39   8.855%   $264.9422   $264.94   $264.95   $264.90  
  Purchase #3 $147.66   4.254%   $153.9415   $153.94   $153.95   $153.90  
  Purchase #4 $237.99   6.133%   $252.5859   $252.59   $252.60   $252.60  
  Purchase #5 $133.25   11.225%   $148.2073   $148.21   $148.20   $148.20  
  Purchase #6 $193.58   3.392%   $200.1462   $200.15   $200.15   $200.10  
  Purchase #7 $90.31   4.850%   $94.69   $94.69   $94.70   $94.70  
  7 purchase totals = $1,258.59       $1,349.8251   $1,349.83   $1,349.85   $1,349.70