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 $60.87   10.475%   $67.2461   $67.25   $67.25   $67.20  
  Purchase #2 $114.31   11.854%   $127.8603   $127.86   $127.85   $127.90  
  Purchase #3 $171.53   12.456%   $192.8958   $192.90   $192.90   $192.90  
  Purchase #4 $69.70   11.577%   $77.7692   $77.77   $77.75   $77.80  
  Purchase #5 $12.90   12.843%   $14.5567   $14.56   $14.55   $14.60  
  Purchase #6 $232.61   8.497%   $252.3749   $252.37   $252.35   $252.40  
  Purchase #7 $150.67   10.693%   $166.7811   $166.78   $166.80   $166.80  
  7 purchase totals = $812.59       $899.4841   $899.49   $899.45   $899.60