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 $68.36   13.332%   $77.4738   $77.47   $77.45   $77.50  
  Purchase #2 $192.63   4.458%   $201.2174   $201.22   $201.20   $201.20  
  Purchase #3 $121.35   8.499%   $131.6635   $131.66   $131.65   $131.70  
  Purchase #4 $234.80   6.647%   $250.4072   $250.41   $250.40   $250.40  
  Purchase #5 $247.80   13.679%   $281.6966   $281.70   $281.70   $281.70  
  Purchase #6 $141.51   4.240%   $147.51   $147.51   $147.50   $147.50  
  Purchase #7 $119.54   5.781%   $126.4506   $126.45   $126.45   $126.50  
  7 purchase totals = $1,125.99       $1,216.4191   $1,216.42   $1,216.35   $1,216.50