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 $243.98   7.368%   $261.9564   $261.96   $261.95   $262.00  
  Purchase #2 $203.68   8.265%   $220.5142   $220.51   $220.50   $220.50  
  Purchase #3 $235.90   10.860%   $261.5187   $261.52   $261.50   $261.50  
  Purchase #4 $211.70   12.657%   $238.4949   $238.49   $238.50   $238.50  
  Purchase #5 $80.67   5.427%   $85.048   $85.05   $85.05   $85.00  
  Purchase #6 $234.63   3.252%   $242.2602   $242.26   $242.25   $242.30  
  Purchase #7 $197.72   9.314%   $216.1356   $216.14   $216.15   $216.10  
  7 purchase totals = $1,408.28       $1,525.9280   $1,525.93   $1,525.90   $1,525.90