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 $63.41   5.778%   $67.0738   $67.07   $67.05   $67.10  
  Purchase #2 $198.80   3.270%   $205.3008   $205.30   $205.30   $205.30  
  Purchase #3 $238.84   9.514%   $261.5632   $261.56   $261.55   $261.60  
  Purchase #4 $232.97   11.106%   $258.8436   $258.84   $258.85   $258.80  
  Purchase #5 $181.33   3.653%   $187.954   $187.95   $187.95   $188.00  
  Purchase #6 $167.34   11.147%   $185.9934   $185.99   $186.00   $186.00  
  Purchase #7 $191.95   12.136%   $215.2451   $215.25   $215.25   $215.20  
  7 purchase totals = $1,274.64       $1,381.9739   $1,381.96   $1,381.95   $1,382.00