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 $62.85   10.387%   $69.3782   $69.38   $69.40   $69.40  
  Purchase #2 $185.62   8.868%   $202.0808   $202.08   $202.10   $202.10  
  Purchase #3 $229.64   7.341%   $246.4979   $246.50   $246.50   $246.50  
  Purchase #4 $71.59   6.302%   $76.1016   $76.10   $76.10   $76.10  
  Purchase #5 $114.54   5.571%   $120.921   $120.92   $120.90   $120.90  
  Purchase #6 $149.83   4.357%   $156.3581   $156.36   $156.35   $156.40  
  Purchase #7 $144.45   13.129%   $163.4148   $163.41   $163.40   $163.40  
  7 purchase totals = $958.52       $1,034.7524   $1,034.75   $1,034.75   $1,034.80