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 $192.73   9.513%   $211.0644   $211.06   $211.05   $211.10  
  Purchase #2 $214.52   9.746%   $235.4271   $235.43   $235.45   $235.40  
  Purchase #3 $42.80   9.376%   $46.8129   $46.81   $46.80   $46.80  
  Purchase #4 $79.44   6.726%   $84.7831   $84.78   $84.80   $84.80  
  Purchase #5 $202.81   9.183%   $221.434   $221.43   $221.45   $221.40  
  Purchase #6 $206.30   13.797%   $234.7632   $234.76   $234.75   $234.80  
  Purchase #7 $200.89   13.580%   $228.1709   $228.17   $228.15   $228.20  
  7 purchase totals = $1,139.49       $1,262.4556   $1,262.44   $1,262.45   $1,262.50