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 $62.32   7.723%   $67.133   $67.13   $67.15   $67.10  
  Purchase #2 $177.89   12.239%   $199.662   $199.66   $199.65   $199.70  
  Purchase #3 $134.99   9.150%   $147.3416   $147.34   $147.35   $147.30  
  Purchase #4 $226.65   9.745%   $248.737   $248.74   $248.75   $248.70  
  Purchase #5 $34.25   5.228%   $36.0406   $36.04   $36.05   $36.00  
  Purchase #6 $171.72   5.815%   $181.7055   $181.71   $181.70   $181.70  
  Purchase #7 $204.56   13.439%   $232.0508   $232.05   $232.05   $232.10  
  7 purchase totals = $1,012.38       $1,112.6705   $1,112.67   $1,112.70   $1,112.60