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 $41.77   13.196%   $47.282   $47.28   $47.30   $47.30  
  Purchase #2 $233.49   10.861%   $258.8493   $258.85   $258.85   $258.80  
  Purchase #3 $80.58   6.739%   $86.0103   $86.01   $86.00   $86.00  
  Purchase #4 $163.96   12.664%   $184.7239   $184.72   $184.70   $184.70  
  Purchase #5 $163.76   13.635%   $186.0887   $186.09   $186.10   $186.10  
  Purchase #6 $107.50   6.128%   $114.0876   $114.09   $114.10   $114.10  
  Purchase #7 $156.99   8.297%   $170.0155   $170.02   $170.00   $170.00  
  7 purchase totals = $948.05       $1,047.0573   $1,047.06   $1,047.05   $1,047.00