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 $164.55   10.615%   $182.017   $182.02   $182.00   $182.00  
  Purchase #2 $216.51   13.655%   $246.0744   $246.07   $246.05   $246.10  
  Purchase #3 $229.88   7.401%   $246.8934   $246.89   $246.90   $246.90  
  Purchase #4 $85.38   8.482%   $92.6219   $92.62   $92.60   $92.60  
  Purchase #5 $172.72   6.420%   $183.8086   $183.81   $183.80   $183.80  
  Purchase #6 $124.53   9.164%   $135.9419   $135.94   $135.95   $135.90  
  Purchase #7 $224.48   11.657%   $250.6476   $250.65   $250.65   $250.60  
  7 purchase totals = $1,218.05       $1,338.0048   $1,338.00   $1,337.95   $1,337.90