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 $53.67   11.422%   $59.8002   $59.80   $59.80   $59.80  
  Purchase #2 $217.99   3.478%   $225.5717   $225.57   $225.55   $225.60  
  Purchase #3 $206.77   3.137%   $213.2564   $213.26   $213.25   $213.30  
  Purchase #4 $206.94   10.176%   $227.9982   $228.00   $228.00   $228.00  
  Purchase #5 $178.76   12.261%   $200.6778   $200.68   $200.70   $200.70  
  Purchase #6 $6.38   6.147%   $6.7722   $6.77   $6.75   $6.80  
  Purchase #7 $197.25   8.219%   $213.462   $213.46   $213.45   $213.50  
  7 purchase totals = $1,067.76       $1,147.5385   $1,147.54   $1,147.50   $1,147.70