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 $184.83   11.619%   $206.3054   $206.31   $206.30   $206.30  
  Purchase #2 $12.67   7.595%   $13.6323   $13.63   $13.65   $13.60  
  Purchase #3 $188.43   6.305%   $200.3105   $200.31   $200.30   $200.30  
  Purchase #4 $121.41   4.237%   $126.5541   $126.55   $126.55   $126.60  
  Purchase #5 $182.60   8.871%   $198.7984   $198.80   $198.80   $198.80  
  Purchase #6 $142.73   8.834%   $155.3388   $155.34   $155.35   $155.30  
  Purchase #7 $120.81   3.122%   $124.5817   $124.58   $124.60   $124.60  
  7 purchase totals = $953.48       $1,025.5212   $1,025.52   $1,025.55   $1,025.50