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 $211.97   5.205%   $223.003   $223.00   $223.00   $223.00  
  Purchase #2 $127.86   5.341%   $134.689   $134.69   $134.70   $134.70  
  Purchase #3 $241.28   8.267%   $261.2266   $261.23   $261.25   $261.20  
  Purchase #4 $129.61   12.400%   $145.6816   $145.68   $145.70   $145.70  
  Purchase #5 $229.89   8.340%   $249.0628   $249.06   $249.05   $249.10  
  Purchase #6 $59.49   6.512%   $63.364   $63.36   $63.35   $63.40  
  Purchase #7 $230.30   8.319%   $249.4587   $249.46   $249.45   $249.50  
  7 purchase totals = $1,230.40       $1,326.4857   $1,326.48   $1,326.50   $1,326.60