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 $187.97   5.816%   $198.9023   $198.90   $198.90   $198.90  
  Purchase #2 $195.51   5.187%   $205.6511   $205.65   $205.65   $205.70  
  Purchase #3 $131.46   3.576%   $136.161   $136.16   $136.15   $136.20  
  Purchase #4 $53.71   6.640%   $57.2763   $57.28   $57.30   $57.30  
  Purchase #5 $218.58   7.591%   $235.1724   $235.17   $235.15   $235.20  
  Purchase #6 $60.33   9.205%   $65.8834   $65.88   $65.90   $65.90  
  Purchase #7 $166.95   6.140%   $177.2007   $177.20   $177.20   $177.20  
  7 purchase totals = $1,014.51       $1,076.2472   $1,076.24   $1,076.25   $1,076.40