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 $241.53   11.376%   $269.0065   $269.01   $269.00   $269.00  
  Purchase #2 $238.39   9.279%   $260.5102   $260.51   $260.50   $260.50  
  Purchase #3 $45.70   13.451%   $51.8471   $51.85   $51.85   $51.80  
  Purchase #4 $231.84   4.105%   $241.357   $241.36   $241.35   $241.40  
  Purchase #5 $26.60   12.517%   $29.9295   $29.93   $29.95   $29.90  
  Purchase #6 $63.83   12.604%   $71.8751   $71.88   $71.90   $71.90  
  Purchase #7 $207.44   5.623%   $219.1044   $219.10   $219.10   $219.10  
  7 purchase totals = $1,055.33       $1,143.6298   $1,143.64   $1,143.65   $1,143.60