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 $64.89   5.153%   $68.2338   $68.23   $68.25   $68.20  
  Purchase #2 $109.97   7.282%   $117.978   $117.98   $118.00   $118.00  
  Purchase #3 $111.89   9.571%   $122.599   $122.60   $122.60   $122.60  
  Purchase #4 $168.50   5.363%   $177.5367   $177.54   $177.55   $177.50  
  Purchase #5 $230.46   8.144%   $249.2287   $249.23   $249.25   $249.20  
  Purchase #6 $176.27   9.588%   $193.1708   $193.17   $193.15   $193.20  
  Purchase #7 $130.44   6.455%   $138.8599   $138.86   $138.85   $138.90  
  7 purchase totals = $992.42       $1,067.6069   $1,067.61   $1,067.65   $1,067.60