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 $233.75   8.318%   $253.1933   $253.19   $253.20   $253.20  
  Purchase #2 $164.25   6.183%   $174.4056   $174.41   $174.40   $174.40  
  Purchase #3 $218.58   12.534%   $245.9768   $245.98   $246.00   $246.00  
  Purchase #4 $77.47   3.430%   $80.1272   $80.13   $80.15   $80.10  
  Purchase #5 $192.81   6.320%   $204.9956   $205.00   $205.00   $205.00  
  Purchase #6 $53.40   10.131%   $58.81   $58.81   $58.80   $58.80  
  Purchase #7 $119.44   10.857%   $132.4076   $132.41   $132.40   $132.40  
  7 purchase totals = $1,059.70       $1,149.9161   $1,149.93   $1,149.95   $1,149.90