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 $60.36   3.136%   $62.2529   $62.25   $62.25   $62.30  
  Purchase #2 $205.49   9.565%   $225.1451   $225.15   $225.15   $225.10  
  Purchase #3 $33.37   6.156%   $35.4243   $35.42   $35.40   $35.40  
  Purchase #4 $209.49   13.340%   $237.436   $237.44   $237.45   $237.40  
  Purchase #5 $110.41   7.547%   $118.7426   $118.74   $118.75   $118.70  
  Purchase #6 $230.46   7.770%   $248.3667   $248.37   $248.35   $248.40  
  Purchase #7 $130.69   7.207%   $140.1088   $140.11   $140.10   $140.10  
  7 purchase totals = $980.27       $1,067.4764   $1,067.48   $1,067.45   $1,067.40