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 $196.95   10.576%   $217.7794   $217.78   $217.80   $217.80  
  Purchase #2 $128.44   10.831%   $142.3513   $142.35   $142.35   $142.40  
  Purchase #3 $193.63   9.844%   $212.6909   $212.69   $212.70   $212.70  
  Purchase #4 $188.69   5.293%   $198.6774   $198.68   $198.70   $198.70  
  Purchase #5 $246.64   12.426%   $277.2875   $277.29   $277.30   $277.30  
  Purchase #6 $70.49   6.252%   $74.897   $74.90   $74.90   $74.90  
  Purchase #7 $10.30   13.202%   $11.6598   $11.66   $11.65   $11.70  
  7 purchase totals = $1,035.14       $1,135.3433   $1,135.35   $1,135.40   $1,135.50