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 $61.74   5.814%   $65.3296   $65.33   $65.35   $65.30  
  Purchase #2 $185.44   10.596%   $205.0892   $205.09   $205.10   $205.10  
  Purchase #3 $9.46   12.504%   $10.6429   $10.64   $10.65   $10.60  
  Purchase #4 $163.37   12.540%   $183.8566   $183.86   $183.85   $183.90  
  Purchase #5 $184.77   5.616%   $195.1467   $195.15   $195.15   $195.10  
  Purchase #6 $100.30   3.588%   $103.8988   $103.90   $103.90   $103.90  
  Purchase #7 $248.56   7.484%   $267.1622   $267.16   $267.15   $267.20  
  7 purchase totals = $953.64       $1,031.1260   $1,031.13   $1,031.15   $1,031.10