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 $110.62   5.366%   $116.5559   $116.56   $116.55   $116.60  
  Purchase #2 $223.34   8.226%   $241.7119   $241.71   $241.70   $241.70  
  Purchase #3 $242.73   13.732%   $276.0617   $276.06   $276.05   $276.10  
  Purchase #4 $246.73   3.493%   $255.3483   $255.35   $255.35   $255.30  
  Purchase #5 $232.59   7.539%   $250.125   $250.13   $250.15   $250.10  
  Purchase #6 $86.81   10.331%   $95.7783   $95.78   $95.80   $95.80  
  Purchase #7 $240.32   4.305%   $250.6658   $250.67   $250.65   $250.70  
  7 purchase totals = $1,383.14       $1,486.2469   $1,486.26   $1,486.25   $1,486.30