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 $44.79   10.788%   $49.6219   $49.62   $49.60   $49.60  
  Purchase #2 $194.67   6.366%   $207.0627   $207.06   $207.05   $207.10  
  Purchase #3 $54.31   13.429%   $61.6033   $61.60   $61.60   $61.60  
  Purchase #4 $183.56   12.275%   $206.092   $206.09   $206.10   $206.10  
  Purchase #5 $69.47   11.767%   $77.6445   $77.64   $77.65   $77.60  
  Purchase #6 $238.59   3.473%   $246.8762   $246.88   $246.90   $246.90  
  Purchase #7 $12.40   9.410%   $13.5668   $13.57   $13.55   $13.60  
  7 purchase totals = $797.79       $862.4674   $862.46   $862.45   $862.50