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 $164.91   6.184%   $175.108   $175.11   $175.10   $175.10  
  Purchase #2 $214.92   5.129%   $225.9432   $225.94   $225.95   $225.90  
  Purchase #3 $127.89   4.844%   $134.085   $134.09   $134.10   $134.10  
  Purchase #4 $161.96   11.853%   $181.1571   $181.16   $181.15   $181.20  
  Purchase #5 $160.32   10.651%   $177.3957   $177.40   $177.40   $177.40  
  Purchase #6 $72.37   13.112%   $81.8592   $81.86   $81.85   $81.90  
  Purchase #7 $71.58   3.511%   $74.0932   $74.09   $74.10   $74.10  
  7 purchase totals = $973.95       $1,049.6414   $1,049.65   $1,049.65   $1,049.70