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 $58.34   6.383%   $62.0638   $62.06   $62.05   $62.10  
  Purchase #2 $138.26   3.212%   $142.7009   $142.70   $142.70   $142.70  
  Purchase #3 $164.54   7.417%   $176.7439   $176.74   $176.75   $176.70  
  Purchase #4 $24.46   7.627%   $26.3256   $26.33   $26.35   $26.30  
  Purchase #5 $166.49   7.258%   $178.5738   $178.57   $178.55   $178.60  
  Purchase #6 $103.80   7.410%   $111.4916   $111.49   $111.50   $111.50  
  Purchase #7 $217.83   3.645%   $225.7699   $225.77   $225.75   $225.80  
  7 purchase totals = $873.72       $923.6695   $923.66   $923.65   $923.70