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 $202.38   7.457%   $217.4715   $217.47   $217.45   $217.50  
  Purchase #2 $176.52   4.820%   $185.0283   $185.03   $185.05   $185.00  
  Purchase #3 $51.70   13.528%   $58.694   $58.69   $58.70   $58.70  
  Purchase #4 $229.25   4.705%   $240.0362   $240.04   $240.05   $240.00  
  Purchase #5 $94.75   6.696%   $101.0945   $101.09   $101.10   $101.10  
  Purchase #6 $239.32   4.677%   $250.513   $250.51   $250.50   $250.50  
  Purchase #7 $21.46   13.250%   $24.3035   $24.30   $24.30   $24.30  
  7 purchase totals = $1,015.38       $1,077.1410   $1,077.13   $1,077.15   $1,077.10