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 $91.82   4.401%   $95.861   $95.86   $95.85   $95.90  
  Purchase #2 $186.81   9.176%   $203.9517   $203.95   $203.95   $204.00  
  Purchase #3 $39.56   10.382%   $43.6671   $43.67   $43.65   $43.70  
  Purchase #4 $172.63   7.707%   $185.9346   $185.93   $185.95   $185.90  
  Purchase #5 $156.98   11.518%   $175.061   $175.06   $175.05   $175.10  
  Purchase #6 $176.33   9.626%   $193.3035   $193.30   $193.30   $193.30  
  Purchase #7 $58.86   11.367%   $65.5506   $65.55   $65.55   $65.60  
  7 purchase totals = $882.99       $963.3295   $963.32   $963.30   $963.50