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 $58.25   6.504%   $62.0386   $62.04   $62.05   $62.00  
  Purchase #2 $124.27   9.236%   $135.7476   $135.75   $135.75   $135.70  
  Purchase #3 $215.25   5.728%   $227.5795   $227.58   $227.60   $227.60  
  Purchase #4 $123.32   10.556%   $136.3377   $136.34   $136.35   $136.30  
  Purchase #5 $110.64   6.726%   $118.0816   $118.08   $118.10   $118.10  
  Purchase #6 $249.99   5.706%   $264.2544   $264.25   $264.25   $264.30  
  Purchase #7 $250.55   5.429%   $264.1524   $264.15   $264.15   $264.20  
  7 purchase totals = $1,132.27       $1,208.1918   $1,208.19   $1,208.25   $1,208.20