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 $65.65   10.632%   $72.6299   $72.63   $72.65   $72.60  
  Purchase #2 $187.94   7.816%   $202.6294   $202.63   $202.65   $202.60  
  Purchase #3 $230.30   7.732%   $248.1068   $248.11   $248.10   $248.10  
  Purchase #4 $115.94   11.674%   $129.4748   $129.47   $129.45   $129.50  
  Purchase #5 $73.83   8.113%   $79.8198   $79.82   $79.80   $79.80  
  Purchase #6 $237.49   10.379%   $262.1391   $262.14   $262.15   $262.10  
  Purchase #7 $72.78   10.655%   $80.5347   $80.53   $80.55   $80.50  
  7 purchase totals = $983.93       $1,075.3345   $1,075.33   $1,075.35   $1,075.20