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 $68.65   7.560%   $73.8399   $73.84   $73.85   $73.80  
  Purchase #2 $164.62   7.275%   $176.5961   $176.60   $176.60   $176.60  
  Purchase #3 $43.44   12.522%   $48.8796   $48.88   $48.90   $48.90  
  Purchase #4 $205.33   8.338%   $222.4504   $222.45   $222.45   $222.50  
  Purchase #5 $112.81   10.241%   $124.3629   $124.36   $124.35   $124.40  
  Purchase #6 $50.53   3.799%   $52.4496   $52.45   $52.45   $52.40  
  Purchase #7 $166.73   5.775%   $176.3587   $176.36   $176.35   $176.40  
  7 purchase totals = $812.11       $874.9372   $874.94   $874.95   $875.00