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 $173.86   13.433%   $197.2146   $197.21   $197.20   $197.20  
  Purchase #2 $154.98   12.785%   $174.7942   $174.79   $174.80   $174.80  
  Purchase #3 $114.88   3.614%   $119.0318   $119.03   $119.05   $119.00  
  Purchase #4 $241.38   9.820%   $265.0835   $265.08   $265.10   $265.10  
  Purchase #5 $66.28   3.562%   $68.6409   $68.64   $68.65   $68.60  
  Purchase #6 $196.95   5.769%   $208.312   $208.31   $208.30   $208.30  
  Purchase #7 $127.71   11.667%   $142.6099   $142.61   $142.60   $142.60  
  7 purchase totals = $1,076.04       $1,175.6869   $1,175.67   $1,175.70   $1,175.60