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 $176.58   5.677%   $186.6044   $186.60   $186.60   $186.60  
  Purchase #2 $84.66   11.289%   $94.2173   $94.22   $94.20   $94.20  
  Purchase #3 $96.88   6.685%   $103.3564   $103.36   $103.35   $103.40  
  Purchase #4 $46.50   7.665%   $50.0642   $50.06   $50.05   $50.10  
  Purchase #5 $218.94   6.435%   $233.0288   $233.03   $233.05   $233.00  
  Purchase #6 $250.77   7.660%   $269.979   $269.98   $270.00   $270.00  
  Purchase #7 $107.64   3.692%   $111.6141   $111.61   $111.60   $111.60  
  7 purchase totals = $981.97       $1,048.8642   $1,048.86   $1,048.85   $1,048.90