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 $43.35   6.522%   $46.1773   $46.18   $46.20   $46.20  
  Purchase #2 $163.92   10.465%   $181.0742   $181.07   $181.05   $181.10  
  Purchase #3 $205.33   5.652%   $216.9353   $216.94   $216.95   $216.90  
  Purchase #4 $221.69   10.674%   $245.3532   $245.35   $245.35   $245.40  
  Purchase #5 $52.82   5.814%   $55.891   $55.89   $55.90   $55.90  
  Purchase #6 $146.48   4.602%   $153.221   $153.22   $153.20   $153.20  
  Purchase #7 $107.96   6.182%   $114.6341   $114.63   $114.65   $114.60  
  7 purchase totals = $941.55       $1,013.2861   $1,013.28   $1,013.30   $1,013.30