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 $161.41   9.557%   $176.836   $176.84   $176.85   $176.80  
  Purchase #2 $205.47   5.283%   $216.325   $216.33   $216.35   $216.30  
  Purchase #3 $81.88   3.723%   $84.9284   $84.93   $84.95   $84.90  
  Purchase #4 $111.78   9.133%   $121.9889   $121.99   $122.00   $122.00  
  Purchase #5 $190.85   6.242%   $202.7629   $202.76   $202.75   $202.80  
  Purchase #6 $56.88   5.725%   $60.1364   $60.14   $60.15   $60.10  
  Purchase #7 $152.79   5.802%   $161.6549   $161.65   $161.65   $161.70  
  7 purchase totals = $961.06       $1,024.6325   $1,024.64   $1,024.70   $1,024.60