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 $96.97   5.240%   $102.0512   $102.05   $102.05   $102.10  
  Purchase #2 $136.40   10.389%   $150.5706   $150.57   $150.55   $150.60  
  Purchase #3 $52.39   9.294%   $57.2591   $57.26   $57.25   $57.30  
  Purchase #4 $122.80   3.732%   $127.3829   $127.38   $127.40   $127.40  
  Purchase #5 $125.70   6.551%   $133.9346   $133.93   $133.95   $133.90  
  Purchase #6 $201.71   8.521%   $218.8977   $218.90   $218.90   $218.90  
  Purchase #7 $241.29   11.725%   $269.5813   $269.58   $269.60   $269.60  
  7 purchase totals = $977.26       $1,059.6774   $1,059.67   $1,059.70   $1,059.80