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 $211.92   12.157%   $237.6831   $237.68   $237.70   $237.70  
  Purchase #2 $164.89   13.109%   $186.5054   $186.51   $186.50   $186.50  
  Purchase #3 $77.48   3.403%   $80.1166   $80.12   $80.10   $80.10  
  Purchase #4 $52.25   5.192%   $54.9628   $54.96   $54.95   $55.00  
  Purchase #5 $195.29   11.238%   $217.2367   $217.24   $217.25   $217.20  
  Purchase #6 $225.65   4.190%   $235.1047   $235.10   $235.10   $235.10  
  Purchase #7 $170.97   10.800%   $189.4348   $189.43   $189.45   $189.40  
  7 purchase totals = $1,098.45       $1,201.0441   $1,201.04   $1,201.05   $1,201.00