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 $182.66   11.378%   $203.4431   $203.44   $203.45   $203.40  
  Purchase #2 $209.59   13.472%   $237.826   $237.83   $237.85   $237.80  
  Purchase #3 $70.79   9.520%   $77.5292   $77.53   $77.55   $77.50  
  Purchase #4 $177.62   4.804%   $186.1529   $186.15   $186.15   $186.20  
  Purchase #5 $110.55   3.551%   $114.4756   $114.48   $114.50   $114.50  
  Purchase #6 $126.58   5.856%   $133.9925   $133.99   $134.00   $134.00  
  Purchase #7 $88.49   12.597%   $99.6371   $99.64   $99.65   $99.60  
  7 purchase totals = $966.28       $1,053.0564   $1,053.06   $1,053.15   $1,053.00