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 $173.96   4.687%   $182.1135   $182.11   $182.10   $182.10  
  Purchase #2 $52.42   4.684%   $54.8754   $54.88   $54.90   $54.90  
  Purchase #3 $119.80   6.342%   $127.3977   $127.40   $127.40   $127.40  
  Purchase #4 $95.54   9.119%   $104.2523   $104.25   $104.25   $104.30  
  Purchase #5 $185.33   6.767%   $197.8713   $197.87   $197.85   $197.90  
  Purchase #6 $221.55   9.116%   $241.7465   $241.75   $241.75   $241.70  
  Purchase #7 $117.33   6.679%   $125.1665   $125.17   $125.15   $125.20  
  7 purchase totals = $965.93       $1,033.4232   $1,033.43   $1,033.40   $1,033.50