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 $163.97   7.657%   $176.5252   $176.53   $176.55   $176.50  
  Purchase #2 $241.79   10.302%   $266.6992   $266.70   $266.70   $266.70  
  Purchase #3 $227.97   5.779%   $241.1444   $241.14   $241.15   $241.10  
  Purchase #4 $66.76   11.453%   $74.406   $74.41   $74.40   $74.40  
  Purchase #5 $99.76   5.441%   $105.1879   $105.19   $105.20   $105.20  
  Purchase #6 $45.81   5.540%   $48.3479   $48.35   $48.35   $48.30  
  Purchase #7 $240.50   13.193%   $272.2292   $272.23   $272.25   $272.20  
  7 purchase totals = $1,086.56       $1,184.5398   $1,184.55   $1,184.60   $1,184.40