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 $162.71   8.169%   $176.0018   $176.00   $176.00   $176.00  
  Purchase #2 $181.63   9.214%   $198.3654   $198.37   $198.35   $198.40  
  Purchase #3 $121.40   7.867%   $130.9505   $130.95   $130.95   $131.00  
  Purchase #4 $11.61   10.671%   $12.8489   $12.85   $12.85   $12.80  
  Purchase #5 $193.80   10.598%   $214.3389   $214.34   $214.35   $214.30  
  Purchase #6 $135.62   11.182%   $150.785   $150.79   $150.80   $150.80  
  Purchase #7 $132.58   7.749%   $142.8536   $142.85   $142.85   $142.90  
  7 purchase totals = $939.35       $1,026.1441   $1,026.15   $1,026.15   $1,026.20