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 $87.88   8.788%   $95.6029   $95.60   $95.60   $95.60  
  Purchase #2 $234.71   4.670%   $245.671   $245.67   $245.65   $245.70  
  Purchase #3 $236.79   11.616%   $264.2955   $264.30   $264.30   $264.30  
  Purchase #4 $183.25   6.363%   $194.9102   $194.91   $194.90   $194.90  
  Purchase #5 $228.89   9.451%   $250.5224   $250.52   $250.50   $250.50  
  Purchase #6 $50.63   6.254%   $53.7964   $53.80   $53.80   $53.80  
  Purchase #7 $143.36   7.573%   $154.2167   $154.22   $154.20   $154.20  
  7 purchase totals = $1,165.51       $1,259.0151   $1,259.02   $1,258.95   $1,259.00