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 $83.61   13.717%   $95.0788   $95.08   $95.10   $95.10  
  Purchase #2 $94.46   12.216%   $105.9992   $106.00   $106.00   $106.00  
  Purchase #3 $214.64   12.342%   $241.1309   $241.13   $241.15   $241.10  
  Purchase #4 $54.72   4.333%   $57.091   $57.09   $57.10   $57.10  
  Purchase #5 $37.61   9.712%   $41.2627   $41.26   $41.25   $41.30  
  Purchase #6 $70.68   8.184%   $76.4645   $76.46   $76.45   $76.50  
  Purchase #7 $67.94   10.402%   $75.0071   $75.01   $75.00   $75.00  
  7 purchase totals = $623.66       $692.0342   $692.03   $692.05   $692.10