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 $196.69   8.662%   $213.7273   $213.73   $213.75   $213.70  
  Purchase #2 $56.82   5.148%   $59.7451   $59.75   $59.75   $59.70  
  Purchase #3 $134.88   8.699%   $146.6132   $146.61   $146.60   $146.60  
  Purchase #4 $41.63   5.154%   $43.7756   $43.78   $43.80   $43.80  
  Purchase #5 $194.80   3.789%   $202.181   $202.18   $202.20   $202.20  
  Purchase #6 $237.52   3.262%   $245.2679   $245.27   $245.25   $245.30  
  Purchase #7 $117.37   4.359%   $122.4862   $122.49   $122.50   $122.50  
  7 purchase totals = $979.71       $1,033.7963   $1,033.81   $1,033.85   $1,033.80