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 $66.74   8.782%   $72.6011   $72.60   $72.60   $72.60  
  Purchase #2 $88.75   12.301%   $99.6671   $99.67   $99.65   $99.70  
  Purchase #3 $46.57   12.163%   $52.2343   $52.23   $52.25   $52.20  
  Purchase #4 $233.48   6.539%   $248.7473   $248.75   $248.75   $248.70  
  Purchase #5 $35.87   7.337%   $38.5018   $38.50   $38.50   $38.50  
  Purchase #6 $175.45   12.329%   $197.0812   $197.08   $197.10   $197.10  
  Purchase #7 $149.88   11.464%   $167.0622   $167.06   $167.05   $167.10  
  7 purchase totals = $796.74       $875.8950   $875.89   $875.90   $875.90