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 $195.62   9.144%   $213.5075   $213.51   $213.50   $213.50  
  Purchase #2 $49.53   8.443%   $53.7118   $53.71   $53.70   $53.70  
  Purchase #3 $34.61   8.621%   $37.5937   $37.59   $37.60   $37.60  
  Purchase #4 $187.75   7.426%   $201.6923   $201.69   $201.70   $201.70  
  Purchase #5 $188.26   5.563%   $198.7329   $198.73   $198.75   $198.70  
  Purchase #6 $92.43   5.226%   $97.2604   $97.26   $97.25   $97.30  
  Purchase #7 $219.83   11.517%   $245.1478   $245.15   $245.15   $245.10  
  7 purchase totals = $968.03       $1,047.6464   $1,047.64   $1,047.65   $1,047.60