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 $110.60   3.103%   $114.0319   $114.03   $114.05   $114.00  
  Purchase #2 $198.60   3.596%   $205.7417   $205.74   $205.75   $205.70  
  Purchase #3 $55.75   13.473%   $63.2612   $63.26   $63.25   $63.30  
  Purchase #4 $200.87   3.529%   $207.9587   $207.96   $207.95   $208.00  
  Purchase #5 $164.81   9.285%   $180.1126   $180.11   $180.10   $180.10  
  Purchase #6 $26.41   4.283%   $27.5411   $27.54   $27.55   $27.50  
  Purchase #7 $174.52   10.776%   $193.3263   $193.33   $193.35   $193.30  
  7 purchase totals = $931.56       $991.9735   $991.97   $992.00   $991.90