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 $191.93   6.851%   $205.0791   $205.08   $205.10   $205.10  
  Purchase #2 $90.72   12.116%   $101.7116   $101.71   $101.70   $101.70  
  Purchase #3 $56.47   13.450%   $64.0652   $64.07   $64.05   $64.10  
  Purchase #4 $156.58   13.324%   $177.4427   $177.44   $177.45   $177.40  
  Purchase #5 $181.48   4.483%   $189.6157   $189.62   $189.60   $189.60  
  Purchase #6 $187.27   3.271%   $193.3956   $193.40   $193.40   $193.40  
  Purchase #7 $117.79   9.466%   $128.94   $128.94   $128.95   $128.90  
  7 purchase totals = $982.24       $1,060.2499   $1,060.26   $1,060.25   $1,060.20