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 $103.82   7.648%   $111.7602   $111.76   $111.75   $111.80  
  Purchase #2 $171.81   13.284%   $194.6332   $194.63   $194.65   $194.60  
  Purchase #3 $194.35   4.189%   $202.4913   $202.49   $202.50   $202.50  
  Purchase #4 $206.78   10.546%   $228.587   $228.59   $228.60   $228.60  
  Purchase #5 $122.93   11.446%   $137.0006   $137.00   $137.00   $137.00  
  Purchase #6 $67.57   8.491%   $73.3074   $73.31   $73.30   $73.30  
  Purchase #7 $207.46   13.835%   $236.1621   $236.16   $236.15   $236.20  
  7 purchase totals = $1,074.72       $1,183.9418   $1,183.94   $1,183.95   $1,184.00