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 $178.42   10.411%   $196.9953   $197.00   $197.00   $197.00  
  Purchase #2 $224.74   6.821%   $240.0695   $240.07   $240.05   $240.10  
  Purchase #3 $189.61   8.209%   $205.1751   $205.18   $205.20   $205.20  
  Purchase #4 $67.70   8.871%   $73.7057   $73.71   $73.70   $73.70  
  Purchase #5 $85.27   12.153%   $95.6329   $95.63   $95.65   $95.60  
  Purchase #6 $234.27   5.765%   $247.7757   $247.78   $247.80   $247.80  
  Purchase #7 $7.35   3.755%   $7.626   $7.63   $7.65   $7.60  
  7 purchase totals = $987.36       $1,066.9802   $1,067.00   $1,067.05   $1,067.00