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 $177.87   13.454%   $201.8006   $201.80   $201.80   $201.80  
  Purchase #2 $152.29   3.193%   $157.1526   $157.15   $157.15   $157.20  
  Purchase #3 $184.69   5.279%   $194.4398   $194.44   $194.45   $194.40  
  Purchase #4 $240.34   4.774%   $251.8138   $251.81   $251.80   $251.80  
  Purchase #5 $188.35   12.558%   $212.003   $212.00   $212.00   $212.00  
  Purchase #6 $248.36   5.705%   $262.5289   $262.53   $262.55   $262.50  
  Purchase #7 $175.56   10.752%   $194.4362   $194.44   $194.45   $194.40  
  7 purchase totals = $1,367.46       $1,474.1749   $1,474.17   $1,474.20   $1,474.10