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 $60.69   8.114%   $65.6144   $65.61   $65.60   $65.60  
  Purchase #2 $60.25   4.572%   $63.0046   $63.00   $63.00   $63.00  
  Purchase #3 $121.38   10.465%   $134.0824   $134.08   $134.10   $134.10  
  Purchase #4 $151.72   4.246%   $158.162   $158.16   $158.15   $158.20  
  Purchase #5 $158.98   11.197%   $176.781   $176.78   $176.80   $176.80  
  Purchase #6 $224.96   6.608%   $239.8254   $239.83   $239.85   $239.80  
  Purchase #7 $182.93   6.472%   $194.7692   $194.77   $194.75   $194.80  
  7 purchase totals = $960.91       $1,032.2390   $1,032.23   $1,032.25   $1,032.30