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 $40.58   7.608%   $43.6673   $43.67   $43.65   $43.70  
  Purchase #2 $248.43   5.257%   $261.49   $261.49   $261.50   $261.50  
  Purchase #3 $246.92   10.786%   $273.5528   $273.55   $273.55   $273.60  
  Purchase #4 $175.67   5.314%   $185.0051   $185.01   $185.00   $185.00  
  Purchase #5 $8.57   13.695%   $9.7437   $9.74   $9.75   $9.70  
  Purchase #6 $169.52   5.386%   $178.6503   $178.65   $178.65   $178.70  
  Purchase #7 $249.26   11.440%   $277.7753   $277.78   $277.80   $277.80  
  7 purchase totals = $1,138.95       $1,229.8845   $1,229.89   $1,229.90   $1,230.00