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 $173.76   12.189%   $194.9396   $194.94   $194.95   $194.90  
  Purchase #2 $175.50   5.626%   $185.3736   $185.37   $185.35   $185.40  
  Purchase #3 $130.83   7.309%   $140.3924   $140.39   $140.40   $140.40  
  Purchase #4 $208.52   12.559%   $234.708   $234.71   $234.70   $234.70  
  Purchase #5 $64.54   5.457%   $68.0619   $68.06   $68.05   $68.10  
  Purchase #6 $217.49   4.208%   $226.642   $226.64   $226.65   $226.60  
  Purchase #7 $23.57   12.390%   $26.4903   $26.49   $26.50   $26.50  
  7 purchase totals = $994.21       $1,076.6078   $1,076.60   $1,076.60   $1,076.60