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 $189.84   3.501%   $196.4863   $196.49   $196.50   $196.50  
  Purchase #2 $218.37   5.636%   $230.6773   $230.68   $230.70   $230.70  
  Purchase #3 $43.48   6.491%   $46.3023   $46.30   $46.30   $46.30  
  Purchase #4 $207.64   12.468%   $233.5286   $233.53   $233.55   $233.50  
  Purchase #5 $6.61   8.809%   $7.1923   $7.19   $7.20   $7.20  
  Purchase #6 $215.36   5.124%   $226.395   $226.40   $226.40   $226.40  
  Purchase #7 $165.90   12.440%   $186.538   $186.54   $186.55   $186.50  
  7 purchase totals = $1,047.20       $1,127.1198   $1,127.13   $1,127.20   $1,127.10