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 $174.34   11.498%   $194.3856   $194.39   $194.40   $194.40  
  Purchase #2 $64.96   13.420%   $73.6776   $73.68   $73.70   $73.70  
  Purchase #3 $5.49   5.482%   $5.791   $5.79   $5.80   $5.80  
  Purchase #4 $63.79   10.162%   $70.2723   $70.27   $70.25   $70.30  
  Purchase #5 $227.63   8.353%   $246.6439   $246.64   $246.65   $246.60  
  Purchase #6 $163.95   11.869%   $183.4092   $183.41   $183.40   $183.40  
  Purchase #7 $163.95   10.145%   $180.5827   $180.58   $180.60   $180.60  
  7 purchase totals = $864.11       $954.7623   $954.76   $954.80   $954.80