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 $24.60   5.591%   $25.9754   $25.98   $26.00   $26.00  
  Purchase #2 $208.30   4.135%   $216.9132   $216.91   $216.90   $216.90  
  Purchase #3 $79.36   6.582%   $84.5835   $84.58   $84.60   $84.60  
  Purchase #4 $167.84   10.655%   $185.7234   $185.72   $185.70   $185.70  
  Purchase #5 $51.92   7.261%   $55.6899   $55.69   $55.70   $55.70  
  Purchase #6 $157.80   13.575%   $179.2214   $179.22   $179.20   $179.20  
  Purchase #7 $106.93   13.453%   $121.3153   $121.32   $121.30   $121.30  
  7 purchase totals = $796.75       $869.4221   $869.42   $869.40   $869.40