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 $182.95   8.262%   $198.0653   $198.07   $198.05   $198.10  
  Purchase #2 $64.82   13.182%   $73.3646   $73.36   $73.35   $73.40  
  Purchase #3 $227.49   8.486%   $246.7948   $246.79   $246.80   $246.80  
  Purchase #4 $28.85   10.243%   $31.8051   $31.81   $31.80   $31.80  
  Purchase #5 $74.49   4.258%   $77.6618   $77.66   $77.65   $77.70  
  Purchase #6 $246.48   3.412%   $254.8899   $254.89   $254.90   $254.90  
  Purchase #7 $157.90   11.733%   $176.4264   $176.43   $176.45   $176.40  
  7 purchase totals = $982.98       $1,059.0079   $1,059.01   $1,059.00   $1,059.10