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 $62.89   5.774%   $66.5213   $66.52   $66.50   $66.50  
  Purchase #2 $209.92   7.457%   $225.5737   $225.57   $225.55   $225.60  
  Purchase #3 $43.64   6.461%   $46.4596   $46.46   $46.45   $46.50  
  Purchase #4 $220.77   7.325%   $236.9414   $236.94   $236.95   $236.90  
  Purchase #5 $250.53   3.719%   $259.8472   $259.85   $259.85   $259.80  
  Purchase #6 $158.67   11.339%   $176.6616   $176.66   $176.65   $176.70  
  Purchase #7 $183.25   3.377%   $189.4384   $189.44   $189.45   $189.40  
  7 purchase totals = $1,129.67       $1,201.4432   $1,201.44   $1,201.40   $1,201.40