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 $59.41   3.858%   $61.702   $61.70   $61.70   $61.70  
  Purchase #2 $49.91   5.497%   $52.6536   $52.65   $52.65   $52.70  
  Purchase #3 $61.84   11.674%   $69.0592   $69.06   $69.05   $69.10  
  Purchase #4 $44.97   3.347%   $46.4751   $46.48   $46.50   $46.50  
  Purchase #5 $127.59   4.250%   $133.0126   $133.01   $133.00   $133.00  
  Purchase #6 $238.90   12.579%   $268.9512   $268.95   $268.95   $269.00  
  Purchase #7 $33.86   7.814%   $36.5058   $36.51   $36.50   $36.50  
  7 purchase totals = $616.48       $668.3595   $668.36   $668.35   $668.50