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 $24.62   6.146%   $26.1331   $26.13   $26.15   $26.10  
  Purchase #2 $248.69   4.802%   $260.6321   $260.63   $260.65   $260.60  
  Purchase #3 $202.40   10.454%   $223.5589   $223.56   $223.55   $223.60  
  Purchase #4 $191.62   11.151%   $212.9875   $212.99   $213.00   $213.00  
  Purchase #5 $242.42   6.765%   $258.8197   $258.82   $258.80   $258.80  
  Purchase #6 $176.61   11.681%   $197.2398   $197.24   $197.25   $197.20  
  Purchase #7 $22.28   7.339%   $23.9151   $23.92   $23.90   $23.90  
  7 purchase totals = $1,108.64       $1,203.2862   $1,203.29   $1,203.30   $1,203.20