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 $34.95   3.167%   $36.0569   $36.06   $36.05   $36.10  
  Purchase #2 $115.76   4.725%   $121.2297   $121.23   $121.25   $121.20  
  Purchase #3 $158.43   4.610%   $165.7336   $165.73   $165.75   $165.70  
  Purchase #4 $158.44   12.598%   $178.4003   $178.40   $178.40   $178.40  
  Purchase #5 $49.91   5.685%   $52.7474   $52.75   $52.75   $52.70  
  Purchase #6 $239.31   4.602%   $250.323   $250.32   $250.30   $250.30  
  Purchase #7 $138.87   3.414%   $143.611   $143.61   $143.60   $143.60  
  7 purchase totals = $895.67       $948.1019   $948.10   $948.10   $948.00