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 $212.86   5.381%   $224.314   $224.31   $224.30   $224.30  
  Purchase #2 $26.94   10.234%   $29.697   $29.70   $29.70   $29.70  
  Purchase #3 $221.64   6.459%   $235.9557   $235.96   $235.95   $236.00  
  Purchase #4 $126.59   8.273%   $137.0628   $137.06   $137.05   $137.10  
  Purchase #5 $228.72   8.694%   $248.6049   $248.60   $248.60   $248.60  
  Purchase #6 $122.88   6.370%   $130.7075   $130.71   $130.70   $130.70  
  Purchase #7 $129.27   4.148%   $134.6321   $134.63   $134.65   $134.60  
  7 purchase totals = $1,068.90       $1,140.9740   $1,140.97   $1,140.95   $1,141.00