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 $44.29   7.620%   $47.6649   $47.66   $47.65   $47.70  
  Purchase #2 $101.91   10.129%   $112.2325   $112.23   $112.25   $112.20  
  Purchase #3 $38.52   4.724%   $40.3397   $40.34   $40.35   $40.30  
  Purchase #4 $201.92   10.296%   $222.7097   $222.71   $222.70   $222.70  
  Purchase #5 $198.93   6.147%   $211.1582   $211.16   $211.15   $211.20  
  Purchase #6 $65.93   6.476%   $70.1996   $70.20   $70.20   $70.20  
  Purchase #7 $194.91   12.743%   $219.7474   $219.75   $219.75   $219.70  
  7 purchase totals = $846.41       $924.0520   $924.05   $924.05   $924.00