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 $84.91   12.577%   $95.5891   $95.59   $95.60   $95.60  
  Purchase #2 $242.49   11.730%   $270.9341   $270.93   $270.95   $270.90  
  Purchase #3 $114.80   7.701%   $123.6407   $123.64   $123.65   $123.60  
  Purchase #4 $12.53   12.132%   $14.0501   $14.05   $14.05   $14.10  
  Purchase #5 $110.36   13.370%   $125.1151   $125.12   $125.10   $125.10  
  Purchase #6 $105.76   4.663%   $110.6916   $110.69   $110.70   $110.70  
  Purchase #7 $50.39   9.835%   $55.3459   $55.35   $55.35   $55.30  
  7 purchase totals = $721.24       $795.3666   $795.37   $795.40   $795.30