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 $68.66   11.577%   $76.6088   $76.61   $76.60   $76.60  
  Purchase #2 $232.58   10.865%   $257.8498   $257.85   $257.85   $257.80  
  Purchase #3 $239.93   5.508%   $253.1453   $253.15   $253.15   $253.10  
  Purchase #4 $106.46   7.274%   $114.2039   $114.20   $114.20   $114.20  
  Purchase #5 $52.66   11.373%   $58.649   $58.65   $58.65   $58.60  
  Purchase #6 $173.57   6.466%   $184.793   $184.79   $184.80   $184.80  
  Purchase #7 $249.36   3.843%   $258.9429   $258.94   $258.95   $258.90  
  7 purchase totals = $1,123.22       $1,204.1927   $1,204.19   $1,204.20   $1,204.00