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 $152.64   7.187%   $163.6102   $163.61   $163.60   $163.60  
  Purchase #2 $194.77   3.784%   $202.1401   $202.14   $202.15   $202.10  
  Purchase #3 $17.48   6.420%   $18.6022   $18.60   $18.60   $18.60  
  Purchase #4 $24.33   7.139%   $26.0669   $26.07   $26.05   $26.10  
  Purchase #5 $180.70   7.845%   $194.8759   $194.88   $194.90   $194.90  
  Purchase #6 $200.32   11.316%   $222.9882   $222.99   $223.00   $223.00  
  Purchase #7 $167.67   9.707%   $183.9457   $183.95   $183.95   $183.90  
  7 purchase totals = $937.91       $1,012.2292   $1,012.24   $1,012.25   $1,012.20