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 $181.67   7.626%   $195.5242   $195.52   $195.50   $195.50  
  Purchase #2 $75.89   9.368%   $82.9994   $83.00   $83.00   $83.00  
  Purchase #3 $232.95   12.236%   $261.4538   $261.45   $261.45   $261.50  
  Purchase #4 $187.39   6.190%   $198.9894   $198.99   $199.00   $199.00  
  Purchase #5 $58.81   9.747%   $64.5422   $64.54   $64.55   $64.50  
  Purchase #6 $229.84   5.258%   $241.925   $241.93   $241.95   $241.90  
  Purchase #7 $216.86   9.401%   $237.247   $237.25   $237.25   $237.20  
  7 purchase totals = $1,183.41       $1,282.6810   $1,282.68   $1,282.70   $1,282.60