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 $67.74   3.266%   $69.9524   $69.95   $69.95   $70.00  
  Purchase #2 $227.35   3.833%   $236.0643   $236.06   $236.05   $236.10  
  Purchase #3 $237.63   4.397%   $248.0786   $248.08   $248.10   $248.10  
  Purchase #4 $165.98   10.761%   $183.8411   $183.84   $183.85   $183.80  
  Purchase #5 $131.50   6.365%   $139.87   $139.87   $139.85   $139.90  
  Purchase #6 $64.26   3.808%   $66.707   $66.71   $66.70   $66.70  
  Purchase #7 $120.52   9.331%   $131.7657   $131.77   $131.75   $131.80  
  7 purchase totals = $1,014.98       $1,076.2791   $1,076.28   $1,076.25   $1,076.40