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 $86.60   11.177%   $96.2793   $96.28   $96.30   $96.30  
  Purchase #2 $182.65   12.429%   $205.3516   $205.35   $205.35   $205.40  
  Purchase #3 $192.37   11.590%   $214.6657   $214.67   $214.65   $214.70  
  Purchase #4 $164.78   4.859%   $172.7867   $172.79   $172.80   $172.80  
  Purchase #5 $89.89   6.476%   $95.7113   $95.71   $95.70   $95.70  
  Purchase #6 $248.44   7.505%   $267.0854   $267.09   $267.10   $267.10  
  Purchase #7 $235.53   4.617%   $246.4044   $246.40   $246.40   $246.40  
  7 purchase totals = $1,200.26       $1,298.2844   $1,298.29   $1,298.30   $1,298.40