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 $115.96   9.183%   $126.6086   $126.61   $126.60   $126.60  
  Purchase #2 $151.36   8.533%   $164.2755   $164.28   $164.30   $164.30  
  Purchase #3 $107.29   11.241%   $119.3505   $119.35   $119.35   $119.40  
  Purchase #4 $203.63   7.795%   $219.503   $219.50   $219.50   $219.50  
  Purchase #5 $205.59   11.488%   $229.2082   $229.21   $229.20   $229.20  
  Purchase #6 $133.51   6.746%   $142.5166   $142.52   $142.50   $142.50  
  Purchase #7 $115.76   7.468%   $124.405   $124.41   $124.40   $124.40  
  7 purchase totals = $1,033.10       $1,125.8674   $1,125.88   $1,125.85   $1,125.90