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 $86.98   7.654%   $93.6374   $93.64   $93.65   $93.60  
  Purchase #2 $108.32   3.173%   $111.757   $111.76   $111.75   $111.80  
  Purchase #3 $117.62   3.687%   $121.9566   $121.96   $121.95   $122.00  
  Purchase #4 $74.73   12.579%   $84.1303   $84.13   $84.15   $84.10  
  Purchase #5 $43.89   5.430%   $46.2732   $46.27   $46.25   $46.30  
  Purchase #6 $237.41   11.664%   $265.1015   $265.10   $265.10   $265.10  
  Purchase #7 $118.59   10.533%   $131.0811   $131.08   $131.10   $131.10  
  7 purchase totals = $787.54       $853.9371   $853.94   $853.95   $854.00