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 $41.26   4.323%   $43.0437   $43.04   $43.05   $43.00  
  Purchase #2 $73.45   5.118%   $77.2092   $77.21   $77.20   $77.20  
  Purchase #3 $195.62   6.323%   $207.9891   $207.99   $208.00   $208.00  
  Purchase #4 $121.61   10.335%   $134.1784   $134.18   $134.20   $134.20  
  Purchase #5 $60.38   11.678%   $67.4312   $67.43   $67.45   $67.40  
  Purchase #6 $247.81   3.375%   $256.1736   $256.17   $256.15   $256.20  
  Purchase #7 $131.64   11.353%   $146.5851   $146.59   $146.60   $146.60  
  7 purchase totals = $871.77       $932.6103   $932.61   $932.65   $932.60