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 $183.32   7.489%   $197.0488   $197.05   $197.05   $197.00  
  Purchase #2 $212.62   13.299%   $240.8963   $240.90   $240.90   $240.90  
  Purchase #3 $245.77   6.266%   $261.1699   $261.17   $261.15   $261.20  
  Purchase #4 $86.79   5.716%   $91.7509   $91.75   $91.75   $91.80  
  Purchase #5 $186.94   13.137%   $211.4983   $211.50   $211.50   $211.50  
  Purchase #6 $165.70   7.359%   $177.8939   $177.89   $177.90   $177.90  
  Purchase #7 $44.64   3.521%   $46.2118   $46.21   $46.20   $46.20  
  7 purchase totals = $1,125.78       $1,226.4699   $1,226.47   $1,226.45   $1,226.50