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 $213.76   5.657%   $225.8524   $225.85   $225.85   $225.90  
  Purchase #2 $23.50   5.515%   $24.796   $24.80   $24.80   $24.80  
  Purchase #3 $38.69   7.452%   $41.5732   $41.57   $41.55   $41.60  
  Purchase #4 $170.34   12.290%   $191.2748   $191.27   $191.25   $191.30  
  Purchase #5 $167.93   4.778%   $175.9537   $175.95   $175.95   $176.00  
  Purchase #6 $218.63   9.412%   $239.2075   $239.21   $239.20   $239.20  
  Purchase #7 $126.62   6.797%   $135.2264   $135.23   $135.25   $135.20  
  7 purchase totals = $959.47       $1,033.8840   $1,033.88   $1,033.85   $1,034.00