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 $32.78   13.623%   $37.2456   $37.25   $37.25   $37.20  
  Purchase #2 $233.84   12.613%   $263.3342   $263.33   $263.35   $263.30  
  Purchase #3 $248.63   11.457%   $277.1155   $277.12   $277.10   $277.10  
  Purchase #4 $41.93   13.512%   $47.5956   $47.60   $47.60   $47.60  
  Purchase #5 $182.96   3.422%   $189.2209   $189.22   $189.20   $189.20  
  Purchase #6 $222.32   4.142%   $231.5285   $231.53   $231.55   $231.50  
  Purchase #7 $27.85   8.321%   $30.1674   $30.17   $30.15   $30.20  
  7 purchase totals = $990.31       $1,076.2077   $1,076.22   $1,076.20   $1,076.10