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 $177.92   11.617%   $198.589   $198.59   $198.60   $198.60  
  Purchase #2 $208.38   9.252%   $227.6593   $227.66   $227.65   $227.70  
  Purchase #3 $142.94   7.493%   $153.6505   $153.65   $153.65   $153.70  
  Purchase #4 $23.77   13.490%   $26.9766   $26.98   $27.00   $27.00  
  Purchase #5 $95.67   11.395%   $106.5716   $106.57   $106.55   $106.60  
  Purchase #6 $104.89   5.359%   $110.5111   $110.51   $110.50   $110.50  
  Purchase #7 $183.89   9.151%   $200.7178   $200.72   $200.70   $200.70  
  7 purchase totals = $937.46       $1,024.6759   $1,024.68   $1,024.65   $1,024.80