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 $56.25   11.592%   $62.7705   $62.77   $62.75   $62.80  
  Purchase #2 $60.38   13.652%   $68.6231   $68.62   $68.60   $68.60  
  Purchase #3 $144.89   13.144%   $163.9343   $163.93   $163.95   $163.90  
  Purchase #4 $192.46   3.263%   $198.74   $198.74   $198.75   $198.70  
  Purchase #5 $199.71   11.377%   $222.431   $222.43   $222.45   $222.40  
  Purchase #6 $218.55   13.126%   $247.2369   $247.24   $247.25   $247.20  
  Purchase #7 $212.94   5.639%   $224.9477   $224.95   $224.95   $224.90  
  7 purchase totals = $1,085.18       $1,188.6835   $1,188.68   $1,188.70   $1,188.50