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 $46.88   4.822%   $49.1406   $49.14   $49.15   $49.10  
  Purchase #2 $157.44   3.224%   $162.5159   $162.52   $162.50   $162.50  
  Purchase #3 $113.90   8.229%   $123.2728   $123.27   $123.25   $123.30  
  Purchase #4 $193.41   4.462%   $202.04   $202.04   $202.05   $202.00  
  Purchase #5 $213.61   12.659%   $240.6509   $240.65   $240.65   $240.70  
  Purchase #6 $168.63   6.478%   $179.5539   $179.55   $179.55   $179.60  
  Purchase #7 $199.52   6.259%   $212.008   $212.01   $212.00   $212.00  
  7 purchase totals = $1,093.39       $1,169.1821   $1,169.18   $1,169.15   $1,169.20