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 $177.34   13.439%   $201.1727   $201.17   $201.15   $201.20  
  Purchase #2 $178.64   10.423%   $197.2596   $197.26   $197.25   $197.30  
  Purchase #3 $206.70   12.659%   $232.8662   $232.87   $232.85   $232.90  
  Purchase #4 $114.73   9.428%   $125.5467   $125.55   $125.55   $125.50  
  Purchase #5 $205.36   10.283%   $226.4772   $226.48   $226.50   $226.50  
  Purchase #6 $54.87   5.399%   $57.8324   $57.83   $57.85   $57.80  
  Purchase #7 $47.54   13.432%   $53.9256   $53.93   $53.95   $53.90  
  7 purchase totals = $985.18       $1,095.0804   $1,095.09   $1,095.10   $1,095.10