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 $184.29   9.693%   $202.1532   $202.15   $202.15   $202.20  
  Purchase #2 $208.87   13.728%   $237.5437   $237.54   $237.55   $237.50  
  Purchase #3 $189.87   8.581%   $206.1627   $206.16   $206.15   $206.20  
  Purchase #4 $222.72   4.312%   $232.3237   $232.32   $232.30   $232.30  
  Purchase #5 $52.93   12.243%   $59.4102   $59.41   $59.40   $59.40  
  Purchase #6 $29.64   7.357%   $31.8206   $31.82   $31.80   $31.80  
  Purchase #7 $206.55   9.864%   $226.9241   $226.92   $226.90   $226.90  
  7 purchase totals = $1,094.87       $1,196.3382   $1,196.32   $1,196.25   $1,196.30