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 $73.41   5.112%   $77.1627   $77.16   $77.15   $77.20  
  Purchase #2 $58.38   6.540%   $62.1981   $62.20   $62.20   $62.20  
  Purchase #3 $211.35   13.109%   $239.0559   $239.06   $239.05   $239.10  
  Purchase #4 $93.90   9.156%   $102.4975   $102.50   $102.50   $102.50  
  Purchase #5 $214.48   4.535%   $224.2067   $224.21   $224.20   $224.20  
  Purchase #6 $202.35   7.627%   $217.7832   $217.78   $217.80   $217.80  
  Purchase #7 $127.83   6.344%   $135.9395   $135.94   $135.95   $135.90  
  7 purchase totals = $981.70       $1,058.8436   $1,058.85   $1,058.85   $1,058.90