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 $246.41   6.260%   $261.8353   $261.84   $261.85   $261.80  
  Purchase #2 $193.81   13.149%   $219.2941   $219.29   $219.30   $219.30  
  Purchase #3 $5.46   12.337%   $6.1336   $6.13   $6.15   $6.10  
  Purchase #4 $74.59   11.546%   $83.2022   $83.20   $83.20   $83.20  
  Purchase #5 $17.40   6.227%   $18.4835   $18.48   $18.50   $18.50  
  Purchase #6 $157.80   13.111%   $178.4892   $178.49   $178.50   $178.50  
  Purchase #7 $243.58   10.469%   $269.0804   $269.08   $269.10   $269.10  
  7 purchase totals = $939.05       $1,036.5183   $1,036.51   $1,036.60   $1,036.50