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 $201.53   11.118%   $223.9361   $223.94   $223.95   $223.90  
  Purchase #2 $142.69   4.212%   $148.7001   $148.70   $148.70   $148.70  
  Purchase #3 $103.33   13.227%   $116.9975   $117.00   $117.00   $117.00  
  Purchase #4 $79.36   4.688%   $83.0804   $83.08   $83.10   $83.10  
  Purchase #5 $129.88   10.780%   $143.8811   $143.88   $143.90   $143.90  
  Purchase #6 $150.90   8.661%   $163.9694   $163.97   $163.95   $164.00  
  Purchase #7 $70.25   3.836%   $72.9448   $72.94   $72.95   $72.90  
  7 purchase totals = $877.94       $953.5094   $953.51   $953.55   $953.50