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 $193.77   7.479%   $208.2621   $208.26   $208.25   $208.30  
  Purchase #2 $169.69   13.830%   $193.1581   $193.16   $193.15   $193.20  
  Purchase #3 $10.26   11.312%   $11.4206   $11.42   $11.40   $11.40  
  Purchase #4 $49.43   6.670%   $52.727   $52.73   $52.75   $52.70  
  Purchase #5 $235.47   13.426%   $267.0842   $267.08   $267.10   $267.10  
  Purchase #6 $80.44   6.649%   $85.7885   $85.79   $85.80   $85.80  
  Purchase #7 $176.81   10.804%   $195.9126   $195.91   $195.90   $195.90  
  7 purchase totals = $915.87       $1,014.3531   $1,014.35   $1,014.35   $1,014.40