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 $24.41   6.771%   $26.0628   $26.06   $26.05   $26.10  
  Purchase #2 $214.42   9.631%   $235.0708   $235.07   $235.05   $235.10  
  Purchase #3 $82.77   4.690%   $86.6519   $86.65   $86.65   $86.70  
  Purchase #4 $71.79   7.790%   $77.3824   $77.38   $77.40   $77.40  
  Purchase #5 $78.91   6.629%   $84.1409   $84.14   $84.15   $84.10  
  Purchase #6 $43.34   11.510%   $48.3284   $48.33   $48.35   $48.30  
  Purchase #7 $218.70   5.205%   $230.0833   $230.08   $230.10   $230.10  
  7 purchase totals = $734.34       $787.7205   $787.71   $787.75   $787.80