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 $193.36   6.364%   $205.6654   $205.67   $205.65   $205.70  
  Purchase #2 $116.64   11.306%   $129.8273   $129.83   $129.85   $129.80  
  Purchase #3 $172.95   13.730%   $196.696   $196.70   $196.70   $196.70  
  Purchase #4 $39.86   9.803%   $43.7675   $43.77   $43.75   $43.80  
  Purchase #5 $154.31   12.415%   $173.4676   $173.47   $173.45   $173.50  
  Purchase #6 $181.80   4.314%   $189.6429   $189.64   $189.65   $189.60  
  Purchase #7 $191.91   6.285%   $203.9715   $203.97   $203.95   $204.00  
  7 purchase totals = $1,050.83       $1,143.0382   $1,143.05   $1,143.00   $1,143.10