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 $206.59   5.182%   $217.2955   $217.30   $217.30   $217.30  
  Purchase #2 $24.69   10.647%   $27.3187   $27.32   $27.30   $27.30  
  Purchase #3 $87.62   6.225%   $93.0743   $93.07   $93.05   $93.10  
  Purchase #4 $79.65   7.235%   $85.4127   $85.41   $85.40   $85.40  
  Purchase #5 $153.37   10.766%   $169.8818   $169.88   $169.90   $169.90  
  Purchase #6 $204.36   9.250%   $223.2633   $223.26   $223.25   $223.30  
  Purchase #7 $196.93   5.841%   $208.4327   $208.43   $208.45   $208.40  
  7 purchase totals = $953.21       $1,024.6790   $1,024.67   $1,024.65   $1,024.70