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 $188.26   7.794%   $202.933   $202.93   $202.95   $202.90  
  Purchase #2 $31.76   4.632%   $33.2311   $33.23   $33.25   $33.20  
  Purchase #3 $123.50   5.807%   $130.6716   $130.67   $130.65   $130.70  
  Purchase #4 $225.97   5.746%   $238.9542   $238.95   $238.95   $239.00  
  Purchase #5 $114.43   10.828%   $126.8205   $126.82   $126.80   $126.80  
  Purchase #6 $197.84   5.349%   $208.4225   $208.42   $208.40   $208.40  
  Purchase #7 $188.87   7.418%   $202.8804   $202.88   $202.90   $202.90  
  7 purchase totals = $1,070.63       $1,143.9133   $1,143.90   $1,143.90   $1,143.90