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 $38.94   11.849%   $43.554   $43.55   $43.55   $43.60  
  Purchase #2 $245.54   6.592%   $261.726   $261.73   $261.75   $261.70  
  Purchase #3 $118.78   13.190%   $134.4471   $134.45   $134.45   $134.40  
  Purchase #4 $198.91   6.398%   $211.6363   $211.64   $211.65   $211.60  
  Purchase #5 $133.98   6.673%   $142.9205   $142.92   $142.90   $142.90  
  Purchase #6 $235.28   3.345%   $243.1501   $243.15   $243.15   $243.20  
  Purchase #7 $53.47   9.464%   $58.5304   $58.53   $58.55   $58.50  
  7 purchase totals = $1,024.90       $1,095.9644   $1,095.97   $1,096.00   $1,095.90