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 $87.33   5.475%   $92.1113   $92.11   $92.10   $92.10  
  Purchase #2 $189.63   9.838%   $208.2858   $208.29   $208.30   $208.30  
  Purchase #3 $37.37   10.861%   $41.4288   $41.43   $41.45   $41.40  
  Purchase #4 $151.93   13.736%   $172.7991   $172.80   $172.80   $172.80  
  Purchase #5 $103.68   8.503%   $112.4959   $112.50   $112.50   $112.50  
  Purchase #6 $234.33   5.813%   $247.9516   $247.95   $247.95   $248.00  
  Purchase #7 $182.30   10.252%   $200.9894   $200.99   $201.00   $201.00  
  7 purchase totals = $986.57       $1,076.0619   $1,076.07   $1,076.10   $1,076.10