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 $220.82   7.871%   $238.2007   $238.20   $238.20   $238.20  
  Purchase #2 $171.45   4.226%   $178.6955   $178.70   $178.70   $178.70  
  Purchase #3 $154.38   8.451%   $167.4267   $167.43   $167.45   $167.40  
  Purchase #4 $142.62   10.259%   $157.2514   $157.25   $157.25   $157.30  
  Purchase #5 $45.86   5.543%   $48.402   $48.40   $48.40   $48.40  
  Purchase #6 $247.58   8.215%   $267.9187   $267.92   $267.90   $267.90  
  Purchase #7 $43.59   6.303%   $46.3375   $46.34   $46.35   $46.30  
  7 purchase totals = $1,026.30       $1,104.2325   $1,104.24   $1,104.25   $1,104.20