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 $192.61   4.693%   $201.6492   $201.65   $201.65   $201.60  
  Purchase #2 $31.76   4.847%   $33.2994   $33.30   $33.30   $33.30  
  Purchase #3 $26.27   7.104%   $28.1362   $28.14   $28.15   $28.10  
  Purchase #4 $68.94   10.403%   $76.1118   $76.11   $76.10   $76.10  
  Purchase #5 $167.50   6.678%   $178.6857   $178.69   $178.70   $178.70  
  Purchase #6 $53.44   3.302%   $55.2046   $55.20   $55.20   $55.20  
  Purchase #7 $199.30   4.793%   $208.8524   $208.85   $208.85   $208.90  
  7 purchase totals = $739.82       $781.9393   $781.94   $781.95   $781.90