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 $90.25   7.722%   $97.2191   $97.22   $97.20   $97.20  
  Purchase #2 $187.44   4.407%   $195.7005   $195.70   $195.70   $195.70  
  Purchase #3 $21.81   8.678%   $23.7027   $23.70   $23.70   $23.70  
  Purchase #4 $152.95   5.489%   $161.3454   $161.35   $161.35   $161.30  
  Purchase #5 $227.70   13.874%   $259.2911   $259.29   $259.30   $259.30  
  Purchase #6 $79.55   12.385%   $89.4023   $89.40   $89.40   $89.40  
  Purchase #7 $118.38   6.746%   $126.3659   $126.37   $126.35   $126.40  
  7 purchase totals = $878.08       $953.0270   $953.03   $953.00   $953.00