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 $101.66   7.532%   $109.317   $109.32   $109.30   $109.30  
  Purchase #2 $246.99   8.246%   $267.3568   $267.36   $267.35   $267.40  
  Purchase #3 $142.39   13.726%   $161.9345   $161.93   $161.95   $161.90  
  Purchase #4 $232.51   7.471%   $249.8808   $249.88   $249.90   $249.90  
  Purchase #5 $235.60   12.737%   $265.6084   $265.61   $265.60   $265.60  
  Purchase #6 $228.61   8.772%   $248.6637   $248.66   $248.65   $248.70  
  Purchase #7 $156.80   6.542%   $167.0579   $167.06   $167.05   $167.10  
  7 purchase totals = $1,344.56       $1,469.8191   $1,469.82   $1,469.80   $1,469.90