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 $62.34   5.483%   $65.7581   $65.76   $65.75   $65.80  
  Purchase #2 $46.61   5.451%   $49.1507   $49.15   $49.15   $49.20  
  Purchase #3 $70.64   12.342%   $79.3584   $79.36   $79.35   $79.40  
  Purchase #4 $161.79   3.528%   $167.498   $167.50   $167.50   $167.50  
  Purchase #5 $14.46   7.825%   $15.5915   $15.59   $15.60   $15.60  
  Purchase #6 $226.70   3.693%   $235.072   $235.07   $235.05   $235.10  
  Purchase #7 $122.78   9.272%   $134.1642   $134.16   $134.15   $134.20  
  7 purchase totals = $705.32       $746.5929   $746.59   $746.55   $746.80