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 $69.57   10.173%   $76.6474   $76.65   $76.65   $76.60  
  Purchase #2 $91.54   12.783%   $103.2416   $103.24   $103.25   $103.20  
  Purchase #3 $113.99   6.739%   $121.6718   $121.67   $121.65   $121.70  
  Purchase #4 $193.75   7.505%   $208.2909   $208.29   $208.30   $208.30  
  Purchase #5 $189.70   6.492%   $202.0153   $202.02   $202.00   $202.00  
  Purchase #6 $183.34   4.427%   $191.4565   $191.46   $191.45   $191.50  
  Purchase #7 $41.93   13.784%   $47.7096   $47.71   $47.70   $47.70  
  7 purchase totals = $883.82       $951.0331   $951.04   $951.00   $951.00