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 $58.80   5.602%   $62.094   $62.09   $62.10   $62.10  
  Purchase #2 $149.91   13.140%   $169.6082   $169.61   $169.60   $169.60  
  Purchase #3 $167.51   10.382%   $184.9009   $184.90   $184.90   $184.90  
  Purchase #4 $193.81   13.674%   $220.3116   $220.31   $220.30   $220.30  
  Purchase #5 $8.34   5.354%   $8.7865   $8.79   $8.80   $8.80  
  Purchase #6 $122.49   10.120%   $134.886   $134.89   $134.90   $134.90  
  Purchase #7 $198.92   6.724%   $212.2954   $212.30   $212.30   $212.30  
  7 purchase totals = $899.78       $992.8826   $992.89   $992.90   $992.90