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 $84.99   12.365%   $95.499   $95.50   $95.50   $95.50  
  Purchase #2 $142.40   13.684%   $161.886   $161.89   $161.90   $161.90  
  Purchase #3 $38.56   10.193%   $42.4904   $42.49   $42.50   $42.50  
  Purchase #4 $145.37   12.597%   $163.6823   $163.68   $163.70   $163.70  
  Purchase #5 $198.58   3.554%   $205.6375   $205.64   $205.65   $205.60  
  Purchase #6 $237.35   13.372%   $269.0884   $269.09   $269.10   $269.10  
  Purchase #7 $29.32   9.197%   $32.0166   $32.02   $32.00   $32.00  
  7 purchase totals = $876.57       $970.3002   $970.31   $970.35   $970.30