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 $88.31   10.262%   $97.3724   $97.37   $97.35   $97.40  
  Purchase #2 $30.68   8.570%   $33.3093   $33.31   $33.30   $33.30  
  Purchase #3 $98.72   13.331%   $111.8804   $111.88   $111.90   $111.90  
  Purchase #4 $106.58   5.735%   $112.6924   $112.69   $112.70   $112.70  
  Purchase #5 $229.98   5.210%   $241.962   $241.96   $241.95   $242.00  
  Purchase #6 $208.26   4.784%   $218.2232   $218.22   $218.20   $218.20  
  Purchase #7 $233.92   7.780%   $252.119   $252.12   $252.10   $252.10  
  7 purchase totals = $996.45       $1,067.5587   $1,067.55   $1,067.50   $1,067.60