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 $217.41   3.349%   $224.6911   $224.69   $224.70   $224.70  
  Purchase #2 $215.94   9.273%   $235.9641   $235.96   $235.95   $236.00  
  Purchase #3 $87.91   10.771%   $97.3788   $97.38   $97.40   $97.40  
  Purchase #4 $68.78   4.508%   $71.8806   $71.88   $71.90   $71.90  
  Purchase #5 $97.68   13.628%   $110.9918   $110.99   $111.00   $111.00  
  Purchase #6 $184.43   7.749%   $198.7215   $198.72   $198.70   $198.70  
  Purchase #7 $211.69   6.699%   $225.8711   $225.87   $225.85   $225.90  
  7 purchase totals = $1,083.84       $1,165.4990   $1,165.49   $1,165.50   $1,165.60