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 $55.46   11.546%   $61.8634   $61.86   $61.85   $61.90  
  Purchase #2 $164.41   6.813%   $175.6113   $175.61   $175.60   $175.60  
  Purchase #3 $45.88   13.451%   $52.0513   $52.05   $52.05   $52.10  
  Purchase #4 $101.59   5.363%   $107.0383   $107.04   $107.05   $107.00  
  Purchase #5 $232.34   3.251%   $239.8934   $239.89   $239.90   $239.90  
  Purchase #6 $11.51   9.787%   $12.6365   $12.64   $12.65   $12.60  
  Purchase #7 $44.78   6.433%   $47.6607   $47.66   $47.65   $47.70  
  7 purchase totals = $655.97       $696.7549   $696.75   $696.75   $696.80