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 $85.75   11.623%   $95.7167   $95.72   $95.70   $95.70  
  Purchase #2 $89.29   13.815%   $101.6254   $101.63   $101.65   $101.60  
  Purchase #3 $246.25   9.624%   $269.9491   $269.95   $269.95   $269.90  
  Purchase #4 $61.64   3.667%   $63.9003   $63.90   $63.90   $63.90  
  Purchase #5 $215.65   3.390%   $222.9605   $222.96   $222.95   $223.00  
  Purchase #6 $108.68   13.578%   $123.4366   $123.44   $123.45   $123.40  
  Purchase #7 $111.88   4.747%   $117.1909   $117.19   $117.20   $117.20  
  7 purchase totals = $919.14       $994.7795   $994.79   $994.80   $994.70