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 $168.37   5.108%   $176.9703   $176.97   $176.95   $177.00  
  Purchase #2 $206.73   4.486%   $216.0039   $216.00   $216.00   $216.00  
  Purchase #3 $14.47   8.489%   $15.6984   $15.70   $15.70   $15.70  
  Purchase #4 $86.75   10.604%   $95.949   $95.95   $95.95   $95.90  
  Purchase #5 $228.52   7.330%   $245.2705   $245.27   $245.25   $245.30  
  Purchase #6 $214.96   12.400%   $241.615   $241.62   $241.60   $241.60  
  Purchase #7 $46.96   11.737%   $52.4717   $52.47   $52.45   $52.50  
  7 purchase totals = $966.76       $1,043.9788   $1,043.98   $1,043.90   $1,044.00