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 $85.39   11.543%   $95.2466   $95.25   $95.25   $95.20  
  Purchase #2 $155.66   12.339%   $174.8669   $174.87   $174.85   $174.90  
  Purchase #3 $39.68   10.237%   $43.742   $43.74   $43.75   $43.70  
  Purchase #4 $96.61   9.270%   $105.5657   $105.57   $105.55   $105.60  
  Purchase #5 $82.45   8.702%   $89.6248   $89.62   $89.60   $89.60  
  Purchase #6 $173.79   11.622%   $193.9879   $193.99   $194.00   $194.00  
  Purchase #7 $52.95   8.115%   $57.2469   $57.25   $57.25   $57.20  
  7 purchase totals = $686.53       $760.2808   $760.29   $760.25   $760.20