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 $92.69   3.511%   $95.9443   $95.94   $95.95   $95.90  
  Purchase #2 $189.36   13.202%   $214.3593   $214.36   $214.35   $214.40  
  Purchase #3 $98.44   10.474%   $108.7506   $108.75   $108.75   $108.80  
  Purchase #4 $237.93   13.247%   $269.4486   $269.45   $269.45   $269.40  
  Purchase #5 $123.39   11.823%   $137.9784   $137.98   $138.00   $138.00  
  Purchase #6 $204.26   4.354%   $213.1535   $213.15   $213.15   $213.20  
  Purchase #7 $183.59   3.816%   $190.5958   $190.60   $190.60   $190.60  
  7 purchase totals = $1,129.66       $1,230.2305   $1,230.23   $1,230.25   $1,230.30