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 $91.94   3.268%   $94.9446   $94.94   $94.95   $94.90  
  Purchase #2 $114.73   11.570%   $128.0043   $128.00   $128.00   $128.00  
  Purchase #3 $228.52   6.161%   $242.5991   $242.60   $242.60   $242.60  
  Purchase #4 $73.73   3.678%   $76.4418   $76.44   $76.45   $76.40  
  Purchase #5 $41.32   13.691%   $46.9771   $46.98   $47.00   $47.00  
  Purchase #6 $84.36   13.782%   $95.9865   $95.99   $96.00   $96.00  
  Purchase #7 $192.90   11.796%   $215.6545   $215.65   $215.65   $215.70  
  7 purchase totals = $827.50       $900.6079   $900.60   $900.65   $900.60