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 $38.67   8.469%   $41.945   $41.95   $41.95   $41.90  
  Purchase #2 $104.57   11.839%   $116.95   $116.95   $116.95   $117.00  
  Purchase #3 $226.98   9.860%   $249.3602   $249.36   $249.35   $249.40  
  Purchase #4 $80.27   9.255%   $87.699   $87.70   $87.70   $87.70  
  Purchase #5 $124.30   13.125%   $140.6144   $140.61   $140.60   $140.60  
  Purchase #6 $171.60   8.228%   $185.7192   $185.72   $185.70   $185.70  
  Purchase #7 $89.32   5.236%   $93.9968   $94.00   $94.00   $94.00  
  7 purchase totals = $835.71       $916.2846   $916.29   $916.25   $916.30