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 $192.40   5.551%   $203.0801   $203.08   $203.10   $203.10  
  Purchase #2 $207.26   8.868%   $225.6398   $225.64   $225.65   $225.60  
  Purchase #3 $210.80   7.536%   $226.6859   $226.69   $226.70   $226.70  
  Purchase #4 $148.85   5.653%   $157.2645   $157.26   $157.25   $157.30  
  Purchase #5 $184.27   11.867%   $206.1373   $206.14   $206.15   $206.10  
  Purchase #6 $186.87   5.259%   $196.6975   $196.70   $196.70   $196.70  
  Purchase #7 $130.62   5.495%   $137.7976   $137.80   $137.80   $137.80  
  7 purchase totals = $1,261.07       $1,353.3027   $1,353.31   $1,353.35   $1,353.30