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 $203.39   6.176%   $215.9514   $215.95   $215.95   $216.00  
  Purchase #2 $34.80   4.618%   $36.4071   $36.41   $36.40   $36.40  
  Purchase #3 $113.39   12.851%   $127.9617   $127.96   $127.95   $128.00  
  Purchase #4 $38.79   6.220%   $41.2027   $41.20   $41.20   $41.20  
  Purchase #5 $49.41   5.161%   $51.9601   $51.96   $51.95   $52.00  
  Purchase #6 $202.55   6.590%   $215.898   $215.90   $215.90   $215.90  
  Purchase #7 $174.59   10.588%   $193.0756   $193.08   $193.10   $193.10  
  7 purchase totals = $816.92       $882.4566   $882.46   $882.45   $882.60