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 $87.41   7.652%   $94.0986   $94.10   $94.10   $94.10  
  Purchase #2 $54.74   6.619%   $58.3632   $58.36   $58.35   $58.40  
  Purchase #3 $78.34   9.428%   $85.7259   $85.73   $85.75   $85.70  
  Purchase #4 $90.76   6.313%   $96.4897   $96.49   $96.50   $96.50  
  Purchase #5 $89.53   6.447%   $95.302   $95.30   $95.30   $95.30  
  Purchase #6 $60.78   13.698%   $69.1056   $69.11   $69.10   $69.10  
  Purchase #7 $113.89   12.116%   $127.6889   $127.69   $127.70   $127.70  
  7 purchase totals = $575.45       $626.7739   $626.78   $626.80   $626.80