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 $53.67   11.414%   $59.7959   $59.80   $59.80   $59.80  
  Purchase #2 $226.97   7.808%   $244.6918   $244.69   $244.70   $244.70  
  Purchase #3 $32.31   6.746%   $34.4896   $34.49   $34.50   $34.50  
  Purchase #4 $199.87   3.749%   $207.3631   $207.36   $207.35   $207.40  
  Purchase #5 $201.42   3.239%   $207.944   $207.94   $207.95   $207.90  
  Purchase #6 $88.85   6.300%   $94.4476   $94.45   $94.45   $94.40  
  Purchase #7 $236.49   11.104%   $262.7498   $262.75   $262.75   $262.70  
  7 purchase totals = $1,039.58       $1,111.4818   $1,111.48   $1,111.50   $1,111.40