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 $175.42   6.163%   $186.2311   $186.23   $186.25   $186.20  
  Purchase #2 $176.33   11.525%   $196.652   $196.65   $196.65   $196.70  
  Purchase #3 $96.78   6.639%   $103.2052   $103.21   $103.20   $103.20  
  Purchase #4 $235.61   8.715%   $256.1434   $256.14   $256.15   $256.10  
  Purchase #5 $32.29   9.263%   $35.281   $35.28   $35.30   $35.30  
  Purchase #6 $190.56   4.320%   $198.7922   $198.79   $198.80   $198.80  
  Purchase #7 $201.66   11.445%   $224.74   $224.74   $224.75   $224.70  
  7 purchase totals = $1,108.65       $1,201.0449   $1,201.04   $1,201.10   $1,201.00