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 $246.47   12.393%   $277.015   $277.02   $277.00   $277.00  
  Purchase #2 $48.87   11.330%   $54.407   $54.41   $54.40   $54.40  
  Purchase #3 $119.61   6.152%   $126.9684   $126.97   $126.95   $127.00  
  Purchase #4 $209.47   7.145%   $224.4366   $224.44   $224.45   $224.40  
  Purchase #5 $82.65   7.677%   $88.995   $89.00   $89.00   $89.00  
  Purchase #6 $63.80   7.129%   $68.3483   $68.35   $68.35   $68.30  
  Purchase #7 $201.64   12.724%   $227.2967   $227.30   $227.30   $227.30  
  7 purchase totals = $972.51       $1,067.4670   $1,067.49   $1,067.45   $1,067.40