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 $113.36   10.728%   $125.5213   $125.52   $125.50   $125.50  
  Purchase #2 $230.47   3.552%   $238.6563   $238.66   $238.65   $238.70  
  Purchase #3 $14.87   3.233%   $15.3507   $15.35   $15.35   $15.40  
  Purchase #4 $246.46   3.621%   $255.3843   $255.38   $255.40   $255.40  
  Purchase #5 $186.44   3.156%   $192.324   $192.32   $192.30   $192.30  
  Purchase #6 $189.30   5.758%   $200.1999   $200.20   $200.20   $200.20  
  Purchase #7 $168.31   3.624%   $174.4096   $174.41   $174.40   $174.40  
  7 purchase totals = $1,149.21       $1,201.8461   $1,201.84   $1,201.80   $1,201.90