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 $193.32   10.713%   $214.0304   $214.03   $214.05   $214.00  
  Purchase #2 $241.67   9.110%   $263.6861   $263.69   $263.70   $263.70  
  Purchase #3 $59.30   9.742%   $65.077   $65.08   $65.10   $65.10  
  Purchase #4 $185.32   8.467%   $201.011   $201.01   $201.00   $201.00  
  Purchase #5 $184.94   7.695%   $199.1711   $199.17   $199.15   $199.20  
  Purchase #6 $173.53   9.685%   $190.3364   $190.34   $190.35   $190.30  
  Purchase #7 $164.90   10.307%   $181.8962   $181.90   $181.90   $181.90  
  7 purchase totals = $1,202.98       $1,315.2082   $1,315.22   $1,315.25   $1,315.20