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 $249.41   5.154%   $262.2646   $262.26   $262.25   $262.30  
  Purchase #2 $66.93   11.390%   $74.5533   $74.55   $74.55   $74.60  
  Purchase #3 $167.83   10.300%   $185.1165   $185.12   $185.10   $185.10  
  Purchase #4 $162.74   8.385%   $176.3857   $176.39   $176.40   $176.40  
  Purchase #5 $235.56   4.655%   $246.5253   $246.53   $246.55   $246.50  
  Purchase #6 $99.91   3.175%   $103.0821   $103.08   $103.10   $103.10  
  Purchase #7 $107.74   5.650%   $113.8273   $113.83   $113.85   $113.80  
  7 purchase totals = $1,090.12       $1,161.7548   $1,161.76   $1,161.80   $1,161.80