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 $52.76   9.718%   $57.8872   $57.89   $57.90   $57.90  
  Purchase #2 $183.54   6.105%   $194.7451   $194.75   $194.75   $194.70  
  Purchase #3 $39.33   9.804%   $43.1859   $43.19   $43.20   $43.20  
  Purchase #4 $180.61   9.605%   $197.9576   $197.96   $197.95   $198.00  
  Purchase #5 $90.76   6.848%   $96.9752   $96.98   $97.00   $97.00  
  Purchase #6 $192.55   11.435%   $214.5681   $214.57   $214.55   $214.60  
  Purchase #7 $231.46   13.449%   $262.5891   $262.59   $262.60   $262.60  
  7 purchase totals = $971.01       $1,067.9082   $1,067.93   $1,067.95   $1,068.00