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 $136.87   5.654%   $144.6086   $144.61   $144.60   $144.60  
  Purchase #2 $239.77   13.570%   $272.3068   $272.31   $272.30   $272.30  
  Purchase #3 $245.82   4.503%   $256.8893   $256.89   $256.90   $256.90  
  Purchase #4 $147.42   9.688%   $161.702   $161.70   $161.70   $161.70  
  Purchase #5 $101.97   6.211%   $108.3034   $108.30   $108.30   $108.30  
  Purchase #6 $145.40   9.179%   $158.7463   $158.75   $158.75   $158.70  
  Purchase #7 $42.80   8.493%   $46.435   $46.44   $46.45   $46.40  
  7 purchase totals = $1,060.05       $1,148.9914   $1,149.00   $1,149.00   $1,148.90