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 $59.29   4.670%   $62.0588   $62.06   $62.05   $62.10  
  Purchase #2 $122.26   6.312%   $129.9771   $129.98   $130.00   $130.00  
  Purchase #3 $146.90   11.180%   $163.3234   $163.32   $163.30   $163.30  
  Purchase #4 $140.99   3.212%   $145.5186   $145.52   $145.50   $145.50  
  Purchase #5 $8.26   3.565%   $8.5545   $8.55   $8.55   $8.60  
  Purchase #6 $207.34   9.117%   $226.2432   $226.24   $226.25   $226.20  
  Purchase #7 $179.55   10.357%   $198.146   $198.15   $198.15   $198.10  
  7 purchase totals = $864.59       $933.8216   $933.82   $933.80   $933.80