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 $191.69   7.582%   $206.2239   $206.22   $206.20   $206.20  
  Purchase #2 $133.69   10.488%   $147.7114   $147.71   $147.70   $147.70  
  Purchase #3 $239.76   3.351%   $247.7944   $247.79   $247.80   $247.80  
  Purchase #4 $67.53   3.249%   $69.724   $69.72   $69.70   $69.70  
  Purchase #5 $107.95   12.149%   $121.0648   $121.06   $121.05   $121.10  
  Purchase #6 $162.56   7.139%   $174.1652   $174.17   $174.15   $174.20  
  Purchase #7 $156.59   12.393%   $175.9962   $176.00   $176.00   $176.00  
  7 purchase totals = $1,059.77       $1,142.6799   $1,142.67   $1,142.60   $1,142.70