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 $214.50   10.846%   $237.7647   $237.76   $237.75   $237.80  
  Purchase #2 $101.45   3.620%   $105.1225   $105.12   $105.10   $105.10  
  Purchase #3 $52.72   12.386%   $59.2499   $59.25   $59.25   $59.20  
  Purchase #4 $55.75   4.452%   $58.232   $58.23   $58.25   $58.20  
  Purchase #5 $169.89   7.575%   $182.7592   $182.76   $182.75   $182.80  
  Purchase #6 $201.87   4.631%   $211.2186   $211.22   $211.20   $211.20  
  Purchase #7 $206.81   10.804%   $229.1538   $229.15   $229.15   $229.20  
  7 purchase totals = $1,002.99       $1,083.5007   $1,083.49   $1,083.45   $1,083.50