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 $184.26   10.117%   $202.9016   $202.90   $202.90   $202.90  
  Purchase #2 $183.94   4.508%   $192.232   $192.23   $192.25   $192.20  
  Purchase #3 $108.39   11.264%   $120.599   $120.60   $120.60   $120.60  
  Purchase #4 $172.87   3.473%   $178.8738   $178.87   $178.85   $178.90  
  Purchase #5 $102.99   10.709%   $114.0192   $114.02   $114.00   $114.00  
  Purchase #6 $101.33   8.527%   $109.9704   $109.97   $109.95   $110.00  
  Purchase #7 $90.81   5.466%   $95.7737   $95.77   $95.75   $95.80  
  7 purchase totals = $944.59       $1,014.3697   $1,014.36   $1,014.30   $1,014.40