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 $211.95   7.545%   $227.9416   $227.94   $227.95   $227.90  
  Purchase #2 $64.43   4.245%   $67.1651   $67.17   $67.15   $67.20  
  Purchase #3 $171.88   6.522%   $183.09   $183.09   $183.10   $183.10  
  Purchase #4 $190.47   3.673%   $197.466   $197.47   $197.45   $197.50  
  Purchase #5 $22.80   10.547%   $25.2047   $25.20   $25.20   $25.20  
  Purchase #6 $240.81   3.398%   $248.9927   $248.99   $249.00   $249.00  
  Purchase #7 $227.95   3.170%   $235.176   $235.18   $235.20   $235.20  
  7 purchase totals = $1,130.29       $1,185.0361   $1,185.04   $1,185.05   $1,185.10