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 $57.95   5.670%   $61.2358   $61.24   $61.25   $61.20  
  Purchase #2 $163.58   4.581%   $171.0736   $171.07   $171.05   $171.10  
  Purchase #3 $238.57   7.867%   $257.3383   $257.34   $257.35   $257.30  
  Purchase #4 $106.91   4.734%   $111.9711   $111.97   $111.95   $112.00  
  Purchase #5 $119.43   12.129%   $133.9157   $133.92   $133.90   $133.90  
  Purchase #6 $110.98   11.777%   $124.0501   $124.05   $124.05   $124.10  
  Purchase #7 $169.50   8.536%   $183.9685   $183.97   $183.95   $184.00  
  7 purchase totals = $966.92       $1,043.5531   $1,043.56   $1,043.50   $1,043.60