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 $23.35   5.316%   $24.5913   $24.59   $24.60   $24.60  
  Purchase #2 $167.39   5.231%   $176.1462   $176.15   $176.15   $176.10  
  Purchase #3 $120.82   10.619%   $133.6499   $133.65   $133.65   $133.60  
  Purchase #4 $240.37   9.684%   $263.6474   $263.65   $263.65   $263.60  
  Purchase #5 $57.69   6.810%   $61.6187   $61.62   $61.60   $61.60  
  Purchase #6 $192.64   11.433%   $214.6645   $214.66   $214.65   $214.70  
  Purchase #7 $161.39   13.236%   $182.7516   $182.75   $182.75   $182.80  
  7 purchase totals = $963.65       $1,057.0696   $1,057.07   $1,057.05   $1,057.00