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 $204.31   4.136%   $212.7603   $212.76   $212.75   $212.80  
  Purchase #2 $161.97   10.626%   $179.1809   $179.18   $179.20   $179.20  
  Purchase #3 $208.47   7.446%   $223.9927   $223.99   $224.00   $224.00  
  Purchase #4 $101.26   3.398%   $104.7008   $104.70   $104.70   $104.70  
  Purchase #5 $185.45   3.423%   $191.798   $191.80   $191.80   $191.80  
  Purchase #6 $146.65   12.370%   $164.7906   $164.79   $164.80   $164.80  
  Purchase #7 $68.38   11.874%   $76.4994   $76.50   $76.50   $76.50  
  7 purchase totals = $1,076.49       $1,153.7227   $1,153.72   $1,153.75   $1,153.80