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 $110.92   7.266%   $118.9794   $118.98   $119.00   $119.00  
  Purchase #2 $65.84   11.395%   $73.3425   $73.34   $73.35   $73.30  
  Purchase #3 $193.85   8.291%   $209.9221   $209.92   $209.90   $209.90  
  Purchase #4 $246.66   6.676%   $263.127   $263.13   $263.15   $263.10  
  Purchase #5 $216.41   6.316%   $230.0785   $230.08   $230.10   $230.10  
  Purchase #6 $246.28   6.298%   $261.7907   $261.79   $261.80   $261.80  
  Purchase #7 $103.33   10.309%   $113.9823   $113.98   $114.00   $114.00  
  7 purchase totals = $1,183.29       $1,271.2225   $1,271.22   $1,271.30   $1,271.20