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 $98.76   7.257%   $105.927   $105.93   $105.95   $105.90  
  Purchase #2 $200.52   8.562%   $217.6885   $217.69   $217.70   $217.70  
  Purchase #3 $54.32   8.159%   $58.752   $58.75   $58.75   $58.80  
  Purchase #4 $215.37   12.820%   $242.9804   $242.98   $243.00   $243.00  
  Purchase #5 $164.35   13.161%   $185.9801   $185.98   $186.00   $186.00  
  Purchase #6 $24.59   11.451%   $27.4058   $27.41   $27.40   $27.40  
  Purchase #7 $106.67   13.783%   $121.3723   $121.37   $121.35   $121.40  
  7 purchase totals = $864.58       $960.1061   $960.11   $960.15   $960.20