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 $219.26   3.391%   $226.6951   $226.70   $226.70   $226.70  
  Purchase #2 $116.74   3.328%   $120.6251   $120.63   $120.65   $120.60  
  Purchase #3 $241.55   4.388%   $252.1492   $252.15   $252.15   $252.10  
  Purchase #4 $80.39   7.117%   $86.1114   $86.11   $86.10   $86.10  
  Purchase #5 $124.53   4.805%   $130.5137   $130.51   $130.50   $130.50  
  Purchase #6 $224.97   8.719%   $244.5851   $244.59   $244.60   $244.60  
  Purchase #7 $92.51   13.367%   $104.8758   $104.88   $104.90   $104.90  
  7 purchase totals = $1,099.95       $1,165.5554   $1,165.57   $1,165.60   $1,165.50