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 $220.86   7.632%   $237.716   $237.72   $237.70   $237.70  
  Purchase #2 $10.69   8.275%   $11.5746   $11.57   $11.55   $11.60  
  Purchase #3 $96.81   10.186%   $106.6711   $106.67   $106.65   $106.70  
  Purchase #4 $118.90   11.109%   $132.1086   $132.11   $132.10   $132.10  
  Purchase #5 $97.84   3.776%   $101.5344   $101.53   $101.55   $101.50  
  Purchase #6 $215.71   11.554%   $240.6331   $240.63   $240.65   $240.60  
  Purchase #7 $216.46   13.673%   $246.0566   $246.06   $246.05   $246.10  
  7 purchase totals = $977.27       $1,076.2944   $1,076.29   $1,076.25   $1,076.30