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 $166.88   5.197%   $175.5528   $175.55   $175.55   $175.60  
  Purchase #2 $223.78   9.392%   $244.7974   $244.80   $244.80   $244.80  
  Purchase #3 $210.48   7.361%   $225.9734   $225.97   $225.95   $226.00  
  Purchase #4 $114.58   9.408%   $125.3597   $125.36   $125.35   $125.40  
  Purchase #5 $185.61   6.829%   $198.2853   $198.29   $198.30   $198.30  
  Purchase #6 $116.93   4.385%   $122.0574   $122.06   $122.05   $122.10  
  Purchase #7 $50.83   3.236%   $52.4749   $52.47   $52.45   $52.50  
  7 purchase totals = $1,069.09       $1,144.5009   $1,144.50   $1,144.45   $1,144.70