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 $68.98   10.541%   $76.2512   $76.25   $76.25   $76.30  
  Purchase #2 $91.65   3.626%   $94.9732   $94.97   $94.95   $95.00  
  Purchase #3 $169.39   11.351%   $188.6175   $188.62   $188.60   $188.60  
  Purchase #4 $90.86   10.558%   $100.453   $100.45   $100.45   $100.50  
  Purchase #5 $140.46   10.788%   $155.6128   $155.61   $155.60   $155.60  
  Purchase #6 $214.57   3.455%   $221.9834   $221.98   $222.00   $222.00  
  Purchase #7 $218.71   9.702%   $239.9292   $239.93   $239.95   $239.90  
  7 purchase totals = $994.62       $1,077.8203   $1,077.81   $1,077.80   $1,077.90