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 $213.57   5.207%   $224.6906   $224.69   $224.70   $224.70  
  Purchase #2 $228.25   7.638%   $245.6837   $245.68   $245.70   $245.70  
  Purchase #3 $221.25   11.461%   $246.6075   $246.61   $246.60   $246.60  
  Purchase #4 $113.44   9.126%   $123.7925   $123.79   $123.80   $123.80  
  Purchase #5 $208.69   10.243%   $230.0661   $230.07   $230.05   $230.10  
  Purchase #6 $155.47   13.755%   $176.8549   $176.85   $176.85   $176.90  
  Purchase #7 $180.48   3.733%   $187.2173   $187.22   $187.20   $187.20  
  7 purchase totals = $1,321.15       $1,434.9126   $1,434.91   $1,434.90   $1,435.00