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 $185.95   5.291%   $195.7886   $195.79   $195.80   $195.80  
  Purchase #2 $38.66   9.373%   $42.2836   $42.28   $42.30   $42.30  
  Purchase #3 $151.46   6.758%   $161.6957   $161.70   $161.70   $161.70  
  Purchase #4 $210.72   12.684%   $237.4477   $237.45   $237.45   $237.40  
  Purchase #5 $139.84   11.295%   $155.6349   $155.63   $155.65   $155.60  
  Purchase #6 $146.99   10.596%   $162.5651   $162.57   $162.55   $162.60  
  Purchase #7 $42.72   6.788%   $45.6198   $45.62   $45.60   $45.60  
  7 purchase totals = $916.34       $1,001.0354   $1,001.04   $1,001.05   $1,001.00