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 $195.45   5.188%   $205.5899   $205.59   $205.60   $205.60  
  Purchase #2 $33.97   6.436%   $36.1563   $36.16   $36.15   $36.20  
  Purchase #3 $48.72   5.168%   $51.2378   $51.24   $51.25   $51.20  
  Purchase #4 $171.75   6.837%   $183.4925   $183.49   $183.50   $183.50  
  Purchase #5 $220.87   6.254%   $234.6832   $234.68   $234.70   $234.70  
  Purchase #6 $110.59   4.440%   $115.5002   $115.50   $115.50   $115.50  
  Purchase #7 $249.96   6.729%   $266.7798   $266.78   $266.80   $266.80  
  7 purchase totals = $1,031.31       $1,093.4397   $1,093.44   $1,093.50   $1,093.50