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 $87.31   10.823%   $96.7596   $96.76   $96.75   $96.80  
  Purchase #2 $227.43   4.151%   $236.8706   $236.87   $236.85   $236.90  
  Purchase #3 $29.91   12.612%   $33.6822   $33.68   $33.70   $33.70  
  Purchase #4 $179.76   7.382%   $193.0299   $193.03   $193.05   $193.00  
  Purchase #5 $53.66   13.228%   $60.7581   $60.76   $60.75   $60.80  
  Purchase #6 $208.29   7.704%   $224.3367   $224.34   $224.35   $224.30  
  Purchase #7 $150.72   11.830%   $168.5502   $168.55   $168.55   $168.60  
  7 purchase totals = $937.08       $1,013.9873   $1,013.99   $1,014.00   $1,014.10