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 $66.41   11.350%   $73.9475   $73.95   $73.95   $73.90  
  Purchase #2 $162.36   12.428%   $182.5381   $182.54   $182.55   $182.50  
  Purchase #3 $29.87   8.702%   $32.4693   $32.47   $32.45   $32.50  
  Purchase #4 $243.68   12.854%   $275.0026   $275.00   $275.00   $275.00  
  Purchase #5 $165.99   3.414%   $171.6569   $171.66   $171.65   $171.70  
  Purchase #6 $191.65   13.396%   $217.3234   $217.32   $217.30   $217.30  
  Purchase #7 $114.86   6.273%   $122.0652   $122.07   $122.05   $122.10  
  7 purchase totals = $974.82       $1,075.0030   $1,075.01   $1,074.95   $1,075.00