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 $118.36   11.563%   $132.046   $132.05   $132.05   $132.00  
  Purchase #2 $62.91   7.792%   $67.8119   $67.81   $67.80   $67.80  
  Purchase #3 $246.44   9.474%   $269.7877   $269.79   $269.80   $269.80  
  Purchase #4 $82.39   10.213%   $90.8045   $90.80   $90.80   $90.80  
  Purchase #5 $246.41   12.716%   $277.7435   $277.74   $277.75   $277.70  
  Purchase #6 $121.28   4.407%   $126.6248   $126.62   $126.60   $126.60  
  Purchase #7 $143.88   12.250%   $161.5053   $161.51   $161.50   $161.50  
  7 purchase totals = $1,021.67       $1,126.3237   $1,126.32   $1,126.30   $1,126.20