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 $198.34   8.196%   $214.5959   $214.60   $214.60   $214.60  
  Purchase #2 $126.59   11.655%   $141.3441   $141.34   $141.35   $141.30  
  Purchase #3 $228.91   11.208%   $254.5662   $254.57   $254.55   $254.60  
  Purchase #4 $186.31   10.543%   $205.9527   $205.95   $205.95   $206.00  
  Purchase #5 $30.43   10.582%   $33.6501   $33.65   $33.65   $33.70  
  Purchase #6 $201.67   9.171%   $220.1652   $220.17   $220.15   $220.20  
  Purchase #7 $240.27   9.524%   $263.1533   $263.15   $263.15   $263.20  
  7 purchase totals = $1,212.52       $1,333.4275   $1,333.43   $1,333.40   $1,333.60