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 $191.43   5.258%   $201.4954   $201.50   $201.50   $201.50  
  Purchase #2 $183.35   10.122%   $201.9087   $201.91   $201.90   $201.90  
  Purchase #3 $19.88   3.148%   $20.5058   $20.51   $20.50   $20.50  
  Purchase #4 $213.30   6.383%   $226.9149   $226.91   $226.90   $226.90  
  Purchase #5 $165.79   10.330%   $182.9161   $182.92   $182.90   $182.90  
  Purchase #6 $73.66   4.425%   $76.9195   $76.92   $76.90   $76.90  
  Purchase #7 $114.36   3.701%   $118.5925   $118.59   $118.60   $118.60  
  7 purchase totals = $961.77       $1,029.2529   $1,029.26   $1,029.20   $1,029.20