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 $50.94   4.543%   $53.2542   $53.25   $53.25   $53.30  
  Purchase #2 $221.76   6.110%   $235.3095   $235.31   $235.30   $235.30  
  Purchase #3 $23.28   3.261%   $24.0392   $24.04   $24.05   $24.00  
  Purchase #4 $91.55   10.504%   $101.1664   $101.17   $101.15   $101.20  
  Purchase #5 $232.81   11.780%   $260.235   $260.24   $260.25   $260.20  
  Purchase #6 $162.78   13.685%   $185.0564   $185.06   $185.05   $185.10  
  Purchase #7 $185.41   8.357%   $200.9047   $200.90   $200.90   $200.90  
  7 purchase totals = $968.53       $1,059.9654   $1,059.97   $1,059.95   $1,060.00