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 $32.62   7.504%   $35.0678   $35.07   $35.05   $35.10  
  Purchase #2 $168.26   6.769%   $179.6495   $179.65   $179.65   $179.60  
  Purchase #3 $114.73   10.726%   $127.0359   $127.04   $127.05   $127.00  
  Purchase #4 $248.33   10.433%   $274.2383   $274.24   $274.25   $274.20  
  Purchase #5 $123.85   13.562%   $140.6465   $140.65   $140.65   $140.60  
  Purchase #6 $192.37   12.258%   $215.9507   $215.95   $215.95   $216.00  
  Purchase #7 $67.54   4.849%   $70.815   $70.82   $70.80   $70.80  
  7 purchase totals = $947.70       $1,043.4037   $1,043.42   $1,043.40   $1,043.30