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 $176.85   5.201%   $186.048   $186.05   $186.05   $186.00  
  Purchase #2 $88.48   4.483%   $92.4466   $92.45   $92.45   $92.40  
  Purchase #3 $14.41   11.185%   $16.0218   $16.02   $16.00   $16.00  
  Purchase #4 $176.69   4.229%   $184.1622   $184.16   $184.15   $184.20  
  Purchase #5 $53.71   6.213%   $57.047   $57.05   $57.05   $57.00  
  Purchase #6 $35.52   5.563%   $37.496   $37.50   $37.50   $37.50  
  Purchase #7 $104.33   4.708%   $109.2419   $109.24   $109.25   $109.20  
  7 purchase totals = $649.99       $682.4635   $682.47   $682.45   $682.30