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 $114.87   9.406%   $125.6747   $125.67   $125.65   $125.70  
  Purchase #2 $139.26   9.548%   $152.5565   $152.56   $152.55   $152.60  
  Purchase #3 $74.57   11.831%   $83.3924   $83.39   $83.40   $83.40  
  Purchase #4 $157.25   10.871%   $174.3446   $174.34   $174.35   $174.30  
  Purchase #5 $126.33   3.520%   $130.7768   $130.78   $130.80   $130.80  
  Purchase #6 $163.94   5.224%   $172.5042   $172.50   $172.50   $172.50  
  Purchase #7 $164.88   6.306%   $175.2773   $175.28   $175.30   $175.30  
  7 purchase totals = $941.10       $1,014.5265   $1,014.52   $1,014.55   $1,014.60