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 $86.74   10.632%   $95.9622   $95.96   $95.95   $96.00  
  Purchase #2 $113.56   8.165%   $122.8322   $122.83   $122.85   $122.80  
  Purchase #3 $208.46   9.157%   $227.5487   $227.55   $227.55   $227.50  
  Purchase #4 $136.38   10.858%   $151.1881   $151.19   $151.20   $151.20  
  Purchase #5 $48.41   7.524%   $52.0524   $52.05   $52.05   $52.10  
  Purchase #6 $244.93   13.333%   $277.5865   $277.59   $277.60   $277.60  
  Purchase #7 $198.53   11.524%   $221.4086   $221.41   $221.40   $221.40  
  7 purchase totals = $1,037.01       $1,148.5787   $1,148.58   $1,148.60   $1,148.60