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 $196.69   5.253%   $207.0221   $207.02   $207.00   $207.00  
  Purchase #2 $84.71   11.511%   $94.461   $94.46   $94.45   $94.50  
  Purchase #3 $127.77   9.734%   $140.2071   $140.21   $140.20   $140.20  
  Purchase #4 $228.25   7.533%   $245.4441   $245.44   $245.45   $245.40  
  Purchase #5 $190.52   12.633%   $214.5884   $214.59   $214.60   $214.60  
  Purchase #6 $74.99   3.644%   $77.7226   $77.72   $77.70   $77.70  
  Purchase #7 $134.45   4.282%   $140.2071   $140.21   $140.20   $140.20  
  7 purchase totals = $1,037.38       $1,119.6524   $1,119.65   $1,119.60   $1,119.60