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 $111.96   12.120%   $125.5296   $125.53   $125.55   $125.50  
  Purchase #2 $147.69   9.184%   $161.2538   $161.25   $161.25   $161.30  
  Purchase #3 $223.37   11.306%   $248.6242   $248.62   $248.60   $248.60  
  Purchase #4 $22.57   12.706%   $25.4377   $25.44   $25.45   $25.40  
  Purchase #5 $165.84   8.433%   $179.8253   $179.83   $179.85   $179.80  
  Purchase #6 $190.32   12.438%   $213.992   $213.99   $214.00   $214.00  
  Purchase #7 $166.41   3.464%   $172.1744   $172.17   $172.15   $172.20  
  7 purchase totals = $1,028.16       $1,126.8370   $1,126.83   $1,126.85   $1,126.80