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 $24.45   7.321%   $26.24   $26.24   $26.25   $26.20  
  Purchase #2 $124.27   9.691%   $136.313   $136.31   $136.30   $136.30  
  Purchase #3 $44.32   4.834%   $46.4624   $46.46   $46.45   $46.50  
  Purchase #4 $239.31   13.320%   $271.1861   $271.19   $271.20   $271.20  
  Purchase #5 $224.98   10.841%   $249.3701   $249.37   $249.35   $249.40  
  Purchase #6 $203.65   4.269%   $212.3438   $212.34   $212.35   $212.30  
  Purchase #7 $173.44   7.114%   $185.7785   $185.78   $185.80   $185.80  
  7 purchase totals = $1,034.42       $1,127.6939   $1,127.69   $1,127.70   $1,127.70