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 $212.63   9.862%   $233.5996   $233.60   $233.60   $233.60  
  Purchase #2 $11.64   9.601%   $12.7576   $12.76   $12.75   $12.80  
  Purchase #3 $76.59   6.179%   $81.3225   $81.32   $81.30   $81.30  
  Purchase #4 $201.83   9.809%   $221.6275   $221.63   $221.65   $221.60  
  Purchase #5 $168.77   7.664%   $181.7045   $181.70   $181.70   $181.70  
  Purchase #6 $212.89   6.237%   $226.1679   $226.17   $226.15   $226.20  
  Purchase #7 $83.61   9.526%   $91.5747   $91.57   $91.55   $91.60  
  7 purchase totals = $967.96       $1,048.7543   $1,048.75   $1,048.70   $1,048.80