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 $183.98   11.594%   $205.3106   $205.31   $205.30   $205.30  
  Purchase #2 $195.76   9.815%   $214.9738   $214.97   $214.95   $215.00  
  Purchase #3 $22.84   13.212%   $25.8576   $25.86   $25.85   $25.90  
  Purchase #4 $84.82   8.484%   $92.0161   $92.02   $92.00   $92.00  
  Purchase #5 $248.61   4.569%   $259.969   $259.97   $259.95   $260.00  
  Purchase #6 $223.70   9.782%   $245.5823   $245.58   $245.60   $245.60  
  Purchase #7 $152.75   6.127%   $162.109   $162.11   $162.10   $162.10  
  7 purchase totals = $1,112.46       $1,205.8184   $1,205.82   $1,205.75   $1,205.90