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 $248.42   5.526%   $262.1477   $262.15   $262.15   $262.10  
  Purchase #2 $203.77   5.608%   $215.1974   $215.20   $215.20   $215.20  
  Purchase #3 $90.67   4.830%   $95.0494   $95.05   $95.05   $95.00  
  Purchase #4 $195.50   5.516%   $206.2838   $206.28   $206.30   $206.30  
  Purchase #5 $111.29   13.711%   $126.549   $126.55   $126.55   $126.50  
  Purchase #6 $83.66   6.481%   $89.082   $89.08   $89.10   $89.10  
  Purchase #7 $194.90   4.744%   $204.1461   $204.15   $204.15   $204.10  
  7 purchase totals = $1,128.21       $1,198.4554   $1,198.46   $1,198.50   $1,198.30