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 $84.28   10.301%   $92.9617   $92.96   $92.95   $93.00  
  Purchase #2 $166.26   10.230%   $183.2684   $183.27   $183.25   $183.30  
  Purchase #3 $97.64   5.541%   $103.0502   $103.05   $103.05   $103.10  
  Purchase #4 $108.40   5.356%   $114.2059   $114.21   $114.20   $114.20  
  Purchase #5 $170.70   12.749%   $192.4625   $192.46   $192.45   $192.50  
  Purchase #6 $151.89   3.506%   $157.2153   $157.22   $157.20   $157.20  
  Purchase #7 $145.48   11.198%   $161.7709   $161.77   $161.75   $161.80  
  7 purchase totals = $924.65       $1,004.9349   $1,004.94   $1,004.85   $1,005.10