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 $43.28   6.831%   $46.2365   $46.24   $46.25   $46.20  
  Purchase #2 $136.71   11.206%   $152.0297   $152.03   $152.05   $152.00  
  Purchase #3 $176.71   11.840%   $197.6325   $197.63   $197.65   $197.60  
  Purchase #4 $152.37   7.418%   $163.6728   $163.67   $163.65   $163.70  
  Purchase #5 $76.85   12.140%   $86.1796   $86.18   $86.20   $86.20  
  Purchase #6 $174.49   7.352%   $187.3185   $187.32   $187.30   $187.30  
  Purchase #7 $171.56   3.493%   $177.5526   $177.55   $177.55   $177.60  
  7 purchase totals = $931.97       $1,010.6222   $1,010.62   $1,010.65   $1,010.60