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 $214.53   12.615%   $241.593   $241.59   $241.60   $241.60  
  Purchase #2 $92.68   11.363%   $103.2112   $103.21   $103.20   $103.20  
  Purchase #3 $87.42   8.784%   $95.099   $95.10   $95.10   $95.10  
  Purchase #4 $164.40   8.840%   $178.933   $178.93   $178.95   $178.90  
  Purchase #5 $94.50   3.231%   $97.5533   $97.55   $97.55   $97.60  
  Purchase #6 $75.77   12.397%   $85.1632   $85.16   $85.15   $85.20  
  Purchase #7 $224.73   7.538%   $241.6701   $241.67   $241.65   $241.70  
  7 purchase totals = $954.03       $1,043.2228   $1,043.21   $1,043.20   $1,043.30