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 $68.83   11.649%   $76.848   $76.85   $76.85   $76.80  
  Purchase #2 $218.64   4.652%   $228.8111   $228.81   $228.80   $228.80  
  Purchase #3 $119.39   12.799%   $134.6707   $134.67   $134.65   $134.70  
  Purchase #4 $180.94   6.653%   $192.9779   $192.98   $193.00   $193.00  
  Purchase #5 $94.43   13.123%   $106.822   $106.82   $106.80   $106.80  
  Purchase #6 $112.31   4.825%   $117.729   $117.73   $117.75   $117.70  
  Purchase #7 $208.45   4.472%   $217.7719   $217.77   $217.75   $217.80  
  7 purchase totals = $1,002.99       $1,075.6306   $1,075.63   $1,075.60   $1,075.60