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 $112.57   11.270%   $125.2566   $125.26   $125.25   $125.30  
  Purchase #2 $200.97   10.757%   $222.5883   $222.59   $222.60   $222.60  
  Purchase #3 $173.68   12.478%   $195.3518   $195.35   $195.35   $195.40  
  Purchase #4 $24.92   6.465%   $26.5311   $26.53   $26.55   $26.50  
  Purchase #5 $248.45   4.388%   $259.352   $259.35   $259.35   $259.40  
  Purchase #6 $53.83   7.645%   $57.9453   $57.95   $57.95   $57.90  
  Purchase #7 $217.94   9.134%   $237.8466   $237.85   $237.85   $237.80  
  7 purchase totals = $1,032.36       $1,124.8717   $1,124.88   $1,124.90   $1,124.90