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 $81.83   13.166%   $92.6037   $92.60   $92.60   $92.60  
  Purchase #2 $142.69   9.157%   $155.7561   $155.76   $155.75   $155.80  
  Purchase #3 $199.75   3.212%   $206.166   $206.17   $206.15   $206.20  
  Purchase #4 $203.66   6.192%   $216.2706   $216.27   $216.25   $216.30  
  Purchase #5 $196.64   13.816%   $223.8078   $223.81   $223.80   $223.80  
  Purchase #6 $12.99   3.387%   $13.43   $13.43   $13.45   $13.40  
  Purchase #7 $43.95   7.642%   $47.3087   $47.31   $47.30   $47.30  
  7 purchase totals = $881.51       $955.3429   $955.35   $955.30   $955.40