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 $58.64   6.167%   $62.2563   $62.26   $62.25   $62.30  
  Purchase #2 $201.72   10.424%   $222.7473   $222.75   $222.75   $222.70  
  Purchase #3 $108.60   10.136%   $119.6077   $119.61   $119.60   $119.60  
  Purchase #4 $231.41   3.192%   $238.7966   $238.80   $238.80   $238.80  
  Purchase #5 $127.47   8.486%   $138.2871   $138.29   $138.30   $138.30  
  Purchase #6 $154.95   5.247%   $163.0802   $163.08   $163.10   $163.10  
  Purchase #7 $179.57   10.359%   $198.1717   $198.17   $198.15   $198.20  
  7 purchase totals = $1,062.36       $1,142.9469   $1,142.96   $1,142.95   $1,143.00