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 $185.45   5.311%   $195.2992   $195.30   $195.30   $195.30  
  Purchase #2 $153.58   11.793%   $171.6917   $171.69   $171.70   $171.70  
  Purchase #3 $45.31   4.397%   $47.3023   $47.30   $47.30   $47.30  
  Purchase #4 $230.31   3.200%   $237.6799   $237.68   $237.70   $237.70  
  Purchase #5 $107.92   5.262%   $113.5988   $113.60   $113.60   $113.60  
  Purchase #6 $42.61   5.751%   $45.0605   $45.06   $45.05   $45.10  
  Purchase #7 $20.70   11.141%   $23.0062   $23.01   $23.00   $23.00  
  7 purchase totals = $785.88       $833.6386   $833.64   $833.65   $833.70