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 $207.53   4.207%   $216.2608   $216.26   $216.25   $216.30  
  Purchase #2 $244.84   12.392%   $275.1806   $275.18   $275.20   $275.20  
  Purchase #3 $142.47   10.630%   $157.6146   $157.61   $157.60   $157.60  
  Purchase #4 $158.97   6.180%   $168.7943   $168.79   $168.80   $168.80  
  Purchase #5 $155.48   4.106%   $161.864   $161.86   $161.85   $161.90  
  Purchase #6 $224.81   12.738%   $253.4463   $253.45   $253.45   $253.40  
  Purchase #7 $225.26   10.816%   $249.6241   $249.62   $249.60   $249.60  
  7 purchase totals = $1,359.36       $1,482.7847   $1,482.77   $1,482.75   $1,482.80