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 $208.81   13.874%   $237.7803   $237.78   $237.80   $237.80  
  Purchase #2 $45.82   11.439%   $51.0613   $51.06   $51.05   $51.10  
  Purchase #3 $91.87   3.332%   $94.9311   $94.93   $94.95   $94.90  
  Purchase #4 $195.98   3.403%   $202.6492   $202.65   $202.65   $202.60  
  Purchase #5 $228.66   8.162%   $247.3232   $247.32   $247.30   $247.30  
  Purchase #6 $182.86   12.583%   $205.8693   $205.87   $205.85   $205.90  
  Purchase #7 $62.94   8.170%   $68.0822   $68.08   $68.10   $68.10  
  7 purchase totals = $1,016.94       $1,107.6966   $1,107.69   $1,107.70   $1,107.70