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 $58.29   8.173%   $63.054   $63.05   $63.05   $63.10  
  Purchase #2 $173.33   10.622%   $191.7411   $191.74   $191.75   $191.70  
  Purchase #3 $120.86   6.686%   $128.9407   $128.94   $128.95   $128.90  
  Purchase #4 $190.40   9.492%   $208.4728   $208.47   $208.45   $208.50  
  Purchase #5 $157.72   10.543%   $174.3484   $174.35   $174.35   $174.30  
  Purchase #6 $5.38   3.470%   $5.5667   $5.57   $5.55   $5.60  
  Purchase #7 $175.39   10.252%   $193.371   $193.37   $193.35   $193.40  
  7 purchase totals = $881.37       $965.4947   $965.49   $965.45   $965.50