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 $43.80   7.566%   $47.1139   $47.11   $47.10   $47.10  
  Purchase #2 $157.43   10.323%   $173.6815   $173.68   $173.70   $173.70  
  Purchase #3 $145.69   10.292%   $160.6844   $160.68   $160.70   $160.70  
  Purchase #4 $208.67   6.759%   $222.774   $222.77   $222.75   $222.80  
  Purchase #5 $7.88   3.619%   $8.1652   $8.17   $8.15   $8.20  
  Purchase #6 $224.34   12.847%   $253.161   $253.16   $253.15   $253.20  
  Purchase #7 $164.42   11.260%   $182.9337   $182.93   $182.95   $182.90  
  7 purchase totals = $952.23       $1,048.5137   $1,048.50   $1,048.50   $1,048.60