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 $214.85   7.775%   $231.5546   $231.55   $231.55   $231.60  
  Purchase #2 $52.26   13.565%   $59.3491   $59.35   $59.35   $59.30  
  Purchase #3 $68.76   11.580%   $76.7224   $76.72   $76.70   $76.70  
  Purchase #4 $199.69   3.191%   $206.0621   $206.06   $206.05   $206.10  
  Purchase #5 $87.76   5.115%   $92.2489   $92.25   $92.25   $92.20  
  Purchase #6 $235.38   8.159%   $254.5847   $254.58   $254.60   $254.60  
  Purchase #7 $178.85   6.255%   $190.0371   $190.04   $190.05   $190.00  
  7 purchase totals = $1,037.55       $1,110.5589   $1,110.55   $1,110.55   $1,110.50