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 $118.83   7.430%   $127.6591   $127.66   $127.65   $127.70  
  Purchase #2 $65.61   11.325%   $73.0403   $73.04   $73.05   $73.00  
  Purchase #3 $49.61   10.336%   $54.7377   $54.74   $54.75   $54.70  
  Purchase #4 $109.71   9.619%   $120.263   $120.26   $120.25   $120.30  
  Purchase #5 $22.89   5.586%   $24.1686   $24.17   $24.15   $24.20  
  Purchase #6 $74.69   3.383%   $77.2168   $77.22   $77.20   $77.20  
  Purchase #7 $228.87   11.419%   $255.0047   $255.00   $255.00   $255.00  
  7 purchase totals = $670.21       $732.0902   $732.09   $732.05   $732.10