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 $185.39   3.614%   $192.09   $192.09   $192.10   $192.10  
  Purchase #2 $110.77   13.182%   $125.3717   $125.37   $125.35   $125.40  
  Purchase #3 $51.61   12.118%   $57.8641   $57.86   $57.85   $57.90  
  Purchase #4 $169.72   12.204%   $190.4326   $190.43   $190.45   $190.40  
  Purchase #5 $226.83   5.441%   $239.1718   $239.17   $239.15   $239.20  
  Purchase #6 $144.32   8.809%   $157.0331   $157.03   $157.05   $157.00  
  Purchase #7 $49.54   6.221%   $52.6219   $52.62   $52.60   $52.60  
  7 purchase totals = $938.18       $1,014.5852   $1,014.57   $1,014.55   $1,014.60