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 $69.61   10.777%   $77.1119   $77.11   $77.10   $77.10  
  Purchase #2 $114.61   9.117%   $125.059   $125.06   $125.05   $125.10  
  Purchase #3 $59.96   12.161%   $67.2517   $67.25   $67.25   $67.30  
  Purchase #4 $186.32   3.108%   $192.1108   $192.11   $192.10   $192.10  
  Purchase #5 $43.46   10.711%   $48.115   $48.12   $48.10   $48.10  
  Purchase #6 $169.93   9.560%   $186.1753   $186.18   $186.20   $186.20  
  Purchase #7 $26.27   13.198%   $29.7371   $29.74   $29.75   $29.70  
  7 purchase totals = $670.16       $725.5608   $725.57   $725.55   $725.60