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 $167.98   9.560%   $184.0389   $184.04   $184.05   $184.00  
  Purchase #2 $227.99   11.407%   $253.9968   $254.00   $254.00   $254.00  
  Purchase #3 $183.57   8.318%   $198.8394   $198.84   $198.85   $198.80  
  Purchase #4 $202.77   5.329%   $213.5756   $213.58   $213.60   $213.60  
  Purchase #5 $54.40   8.820%   $59.1981   $59.20   $59.20   $59.20  
  Purchase #6 $186.59   3.640%   $193.3819   $193.38   $193.40   $193.40  
  Purchase #7 $95.57   10.113%   $105.235   $105.24   $105.25   $105.20  
  7 purchase totals = $1,118.87       $1,208.2657   $1,208.28   $1,208.35   $1,208.20