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 $217.60   11.165%   $241.895   $241.90   $241.90   $241.90  
  Purchase #2 $114.98   5.554%   $121.366   $121.37   $121.35   $121.40  
  Purchase #3 $53.86   11.487%   $60.0469   $60.05   $60.05   $60.00  
  Purchase #4 $12.41   13.713%   $14.1118   $14.11   $14.10   $14.10  
  Purchase #5 $174.85   7.744%   $188.3904   $188.39   $188.40   $188.40  
  Purchase #6 $68.52   8.288%   $74.1989   $74.20   $74.20   $74.20  
  Purchase #7 $93.89   4.214%   $97.8465   $97.85   $97.85   $97.80  
  7 purchase totals = $736.11       $797.8555   $797.87   $797.85   $797.80