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 $222.98   5.839%   $235.9998   $236.00   $236.00   $236.00  
  Purchase #2 $108.89   5.339%   $114.7036   $114.70   $114.70   $114.70  
  Purchase #3 $89.72   3.389%   $92.7606   $92.76   $92.75   $92.80  
  Purchase #4 $23.64   7.192%   $25.3402   $25.34   $25.35   $25.30  
  Purchase #5 $59.35   4.225%   $61.8575   $61.86   $61.85   $61.90  
  Purchase #6 $181.58   7.764%   $195.6779   $195.68   $195.70   $195.70  
  Purchase #7 $96.85   3.279%   $100.0257   $100.03   $100.05   $100.00  
  7 purchase totals = $783.01       $826.3653   $826.37   $826.40   $826.40