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 $87.45   11.635%   $97.6248   $97.62   $97.60   $97.60  
  Purchase #2 $241.56   9.232%   $263.8608   $263.86   $263.85   $263.90  
  Purchase #3 $232.58   7.549%   $250.1375   $250.14   $250.15   $250.10  
  Purchase #4 $134.95   13.725%   $153.4719   $153.47   $153.45   $153.50  
  Purchase #5 $156.48   12.730%   $176.3999   $176.40   $176.40   $176.40  
  Purchase #6 $112.97   9.328%   $123.5078   $123.51   $123.50   $123.50  
  Purchase #7 $187.52   5.416%   $197.6761   $197.68   $197.70   $197.70  
  7 purchase totals = $1,153.51       $1,262.6788   $1,262.68   $1,262.65   $1,262.70