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 $176.83   13.842%   $201.3068   $201.31   $201.30   $201.30  
  Purchase #2 $30.84   12.642%   $34.7388   $34.74   $34.75   $34.70  
  Purchase #3 $94.73   8.255%   $102.55   $102.55   $102.55   $102.60  
  Purchase #4 $29.91   13.849%   $34.0522   $34.05   $34.05   $34.10  
  Purchase #5 $183.47   8.864%   $199.7328   $199.73   $199.75   $199.70  
  Purchase #6 $12.55   3.232%   $12.9556   $12.96   $12.95   $13.00  
  Purchase #7 $151.61   5.397%   $159.7924   $159.79   $159.80   $159.80  
  7 purchase totals = $679.94       $745.1286   $745.13   $745.15   $745.20