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 $169.46   7.743%   $182.5813   $182.58   $182.60   $182.60  
  Purchase #2 $206.98   12.629%   $233.1195   $233.12   $233.10   $233.10  
  Purchase #3 $39.53   8.516%   $42.8964   $42.90   $42.90   $42.90  
  Purchase #4 $160.55   11.702%   $179.3376   $179.34   $179.35   $179.30  
  Purchase #5 $196.66   9.328%   $215.0044   $215.00   $215.00   $215.00  
  Purchase #6 $223.49   8.260%   $241.9503   $241.95   $241.95   $242.00  
  Purchase #7 $166.77   5.750%   $176.3593   $176.36   $176.35   $176.40  
  7 purchase totals = $1,163.44       $1,271.2488   $1,271.25   $1,271.25   $1,271.30