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 $23.97   6.822%   $25.6052   $25.61   $25.60   $25.60  
  Purchase #2 $233.41   10.735%   $258.4666   $258.47   $258.45   $258.50  
  Purchase #3 $240.61   3.315%   $248.5862   $248.59   $248.60   $248.60  
  Purchase #4 $66.50   8.257%   $71.9909   $71.99   $72.00   $72.00  
  Purchase #5 $58.46   6.153%   $62.057   $62.06   $62.05   $62.10  
  Purchase #6 $233.98   4.488%   $244.481   $244.48   $244.50   $244.50  
  Purchase #7 $233.56   10.547%   $258.1936   $258.19   $258.20   $258.20  
  7 purchase totals = $1,090.49       $1,169.3805   $1,169.39   $1,169.40   $1,169.50