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 $194.58   6.217%   $206.677   $206.68   $206.70   $206.70  
  Purchase #2 $172.89   6.501%   $184.1296   $184.13   $184.15   $184.10  
  Purchase #3 $85.46   11.208%   $95.0384   $95.04   $95.05   $95.00  
  Purchase #4 $123.34   9.143%   $134.617   $134.62   $134.60   $134.60  
  Purchase #5 $195.76   6.404%   $208.2965   $208.30   $208.30   $208.30  
  Purchase #6 $67.76   12.181%   $76.0138   $76.01   $76.00   $76.00  
  Purchase #7 $195.65   3.116%   $201.7465   $201.75   $201.75   $201.70  
  7 purchase totals = $1,035.44       $1,106.5188   $1,106.53   $1,106.55   $1,106.40