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 $181.70   13.348%   $205.9533   $205.95   $205.95   $206.00  
  Purchase #2 $108.84   9.768%   $119.4715   $119.47   $119.45   $119.50  
  Purchase #3 $47.48   11.386%   $52.8861   $52.89   $52.90   $52.90  
  Purchase #4 $132.66   8.159%   $143.4837   $143.48   $143.50   $143.50  
  Purchase #5 $88.25   4.252%   $92.0024   $92.00   $92.00   $92.00  
  Purchase #6 $239.55   3.612%   $248.2025   $248.20   $248.20   $248.20  
  Purchase #7 $141.65   7.658%   $152.4976   $152.50   $152.50   $152.50  
  7 purchase totals = $940.13       $1,014.4971   $1,014.49   $1,014.50   $1,014.60