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 $23.83   7.509%   $25.6194   $25.62   $25.60   $25.60  
  Purchase #2 $198.97   9.349%   $217.5717   $217.57   $217.55   $217.60  
  Purchase #3 $10.70   7.861%   $11.5411   $11.54   $11.55   $11.50  
  Purchase #4 $147.51   11.674%   $164.7303   $164.73   $164.75   $164.70  
  Purchase #5 $187.33   4.165%   $195.1323   $195.13   $195.15   $195.10  
  Purchase #6 $51.32   11.565%   $57.2552   $57.26   $57.25   $57.30  
  Purchase #7 $162.64   11.274%   $180.976   $180.98   $181.00   $181.00  
  7 purchase totals = $782.30       $852.8260   $852.83   $852.85   $852.80