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 $225.68   3.463%   $233.4953   $233.50   $233.50   $233.50  
  Purchase #2 $158.43   10.451%   $174.9875   $174.99   $175.00   $175.00  
  Purchase #3 $30.31   12.271%   $34.0293   $34.03   $34.05   $34.00  
  Purchase #4 $197.88   4.441%   $206.6679   $206.67   $206.65   $206.70  
  Purchase #5 $227.75   10.629%   $251.9575   $251.96   $251.95   $252.00  
  Purchase #6 $147.54   3.728%   $153.0403   $153.04   $153.05   $153.00  
  Purchase #7 $56.58   3.102%   $58.3351   $58.34   $58.35   $58.30  
  7 purchase totals = $1,044.17       $1,112.5129   $1,112.53   $1,112.55   $1,112.50