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 $212.76   10.866%   $235.8785   $235.88   $235.90   $235.90  
  Purchase #2 $36.62   10.736%   $40.5515   $40.55   $40.55   $40.60  
  Purchase #3 $59.79   9.246%   $65.3182   $65.32   $65.30   $65.30  
  Purchase #4 $140.25   7.435%   $150.6776   $150.68   $150.70   $150.70  
  Purchase #5 $248.99   6.707%   $265.6898   $265.69   $265.70   $265.70  
  Purchase #6 $86.33   5.750%   $91.294   $91.29   $91.30   $91.30  
  Purchase #7 $97.42   5.220%   $102.5053   $102.51   $102.50   $102.50  
  7 purchase totals = $882.16       $951.9149   $951.92   $951.95   $952.00