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 $165.63   5.135%   $174.1351   $174.14   $174.15   $174.10  
  Purchase #2 $201.90   7.515%   $217.0728   $217.07   $217.05   $217.10  
  Purchase #3 $41.53   12.656%   $46.786   $46.79   $46.80   $46.80  
  Purchase #4 $160.26   9.259%   $175.0985   $175.10   $175.10   $175.10  
  Purchase #5 $98.70   6.688%   $105.3011   $105.30   $105.30   $105.30  
  Purchase #6 $24.95   4.717%   $26.1269   $26.13   $26.15   $26.10  
  Purchase #7 $187.39   11.158%   $208.299   $208.30   $208.30   $208.30  
  7 purchase totals = $880.36       $952.8194   $952.83   $952.85   $952.80