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 $192.66   8.273%   $208.5988   $208.60   $208.60   $208.60  
  Purchase #2 $226.37   3.864%   $235.1169   $235.12   $235.10   $235.10  
  Purchase #3 $163.60   6.440%   $174.1358   $174.14   $174.15   $174.10  
  Purchase #4 $198.42   13.290%   $224.79   $224.79   $224.80   $224.80  
  Purchase #5 $207.34   7.153%   $222.171   $222.17   $222.15   $222.20  
  Purchase #6 $27.62   11.118%   $30.6908   $30.69   $30.70   $30.70  
  Purchase #7 $41.67   7.604%   $44.8386   $44.84   $44.85   $44.80  
  7 purchase totals = $1,057.68       $1,140.3419   $1,140.35   $1,140.35   $1,140.30