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 $82.76   3.838%   $85.9363   $85.94   $85.95   $85.90  
  Purchase #2 $166.67   11.405%   $185.6787   $185.68   $185.70   $185.70  
  Purchase #3 $248.96   8.528%   $270.1913   $270.19   $270.20   $270.20  
  Purchase #4 $234.94   3.236%   $242.5427   $242.54   $242.55   $242.50  
  Purchase #5 $210.33   4.747%   $220.3144   $220.31   $220.30   $220.30  
  Purchase #6 $146.88   11.528%   $163.8123   $163.81   $163.80   $163.80  
  Purchase #7 $54.30   4.385%   $56.6811   $56.68   $56.70   $56.70  
  7 purchase totals = $1,144.84       $1,225.1568   $1,225.15   $1,225.20   $1,225.10