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 $109.86   3.795%   $114.0292   $114.03   $114.05   $114.00  
  Purchase #2 $226.49   11.262%   $251.9973   $252.00   $252.00   $252.00  
  Purchase #3 $35.44   11.558%   $39.5362   $39.54   $39.55   $39.50  
  Purchase #4 $90.29   8.306%   $97.7895   $97.79   $97.80   $97.80  
  Purchase #5 $193.63   3.630%   $200.6588   $200.66   $200.65   $200.70  
  Purchase #6 $199.35   8.112%   $215.5213   $215.52   $215.50   $215.50  
  Purchase #7 $245.55   11.249%   $273.1719   $273.17   $273.15   $273.20  
  7 purchase totals = $1,100.61       $1,192.7042   $1,192.71   $1,192.70   $1,192.70