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 $196.43   3.224%   $202.7629   $202.76   $202.75   $202.80  
  Purchase #2 $118.92   6.527%   $126.6819   $126.68   $126.70   $126.70  
  Purchase #3 $147.56   11.612%   $164.6947   $164.69   $164.70   $164.70  
  Purchase #4 $168.91   7.308%   $181.2539   $181.25   $181.25   $181.30  
  Purchase #5 $188.55   12.124%   $211.4098   $211.41   $211.40   $211.40  
  Purchase #6 $112.29   9.629%   $123.1024   $123.10   $123.10   $123.10  
  Purchase #7 $162.99   3.280%   $168.3361   $168.34   $168.35   $168.30  
  7 purchase totals = $1,095.65       $1,178.2417   $1,178.23   $1,178.25   $1,178.30