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 $195.77   6.349%   $208.1994   $208.20   $208.20   $208.20  
  Purchase #2 $208.29   8.264%   $225.5031   $225.50   $225.50   $225.50  
  Purchase #3 $223.99   5.579%   $236.4864   $236.49   $236.50   $236.50  
  Purchase #4 $164.31   6.586%   $175.1315   $175.13   $175.15   $175.10  
  Purchase #5 $7.36   12.327%   $8.2673   $8.27   $8.25   $8.30  
  Purchase #6 $89.29   5.692%   $94.3724   $94.37   $94.35   $94.40  
  Purchase #7 $73.82   5.162%   $77.6306   $77.63   $77.65   $77.60  
  7 purchase totals = $962.83       $1,025.5907   $1,025.59   $1,025.60   $1,025.60