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 $67.76   7.821%   $73.0595   $73.06   $73.05   $73.10  
  Purchase #2 $217.63   4.284%   $226.9533   $226.95   $226.95   $227.00  
  Purchase #3 $248.48   13.195%   $281.2669   $281.27   $281.25   $281.30  
  Purchase #4 $245.71   9.154%   $268.2023   $268.20   $268.20   $268.20  
  Purchase #5 $192.91   4.231%   $201.072   $201.07   $201.05   $201.10  
  Purchase #6 $79.87   6.483%   $85.048   $85.05   $85.05   $85.00  
  Purchase #7 $218.74   10.149%   $240.9399   $240.94   $240.95   $240.90  
  7 purchase totals = $1,271.10       $1,376.5419   $1,376.54   $1,376.50   $1,376.60