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 $185.69   10.557%   $205.2933   $205.29   $205.30   $205.30  
  Purchase #2 $48.84   11.160%   $54.2905   $54.29   $54.30   $54.30  
  Purchase #3 $197.82   13.361%   $224.2507   $224.25   $224.25   $224.30  
  Purchase #4 $45.28   6.400%   $48.1779   $48.18   $48.20   $48.20  
  Purchase #5 $232.49   12.687%   $261.986   $261.99   $262.00   $262.00  
  Purchase #6 $35.79   10.476%   $39.5394   $39.54   $39.55   $39.50  
  Purchase #7 $245.30   6.730%   $261.8087   $261.81   $261.80   $261.80  
  7 purchase totals = $991.21       $1,095.3465   $1,095.35   $1,095.40   $1,095.40