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 $211.32   11.804%   $236.2642   $236.26   $236.25   $236.30  
  Purchase #2 $238.73   10.191%   $263.059   $263.06   $263.05   $263.10  
  Purchase #3 $148.46   9.518%   $162.5904   $162.59   $162.60   $162.60  
  Purchase #4 $20.93   13.656%   $23.7882   $23.79   $23.80   $23.80  
  Purchase #5 $35.33   3.674%   $36.628   $36.63   $36.65   $36.60  
  Purchase #6 $171.39   8.525%   $186.001   $186.00   $186.00   $186.00  
  Purchase #7 $242.33   9.516%   $265.3901   $265.39   $265.40   $265.40  
  7 purchase totals = $1,068.49       $1,173.7209   $1,173.72   $1,173.75   $1,173.80