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 $82.70   13.256%   $93.6627   $93.66   $93.65   $93.70  
  Purchase #2 $137.82   6.838%   $147.2441   $147.24   $147.25   $147.20  
  Purchase #3 $103.68   5.513%   $109.3959   $109.40   $109.40   $109.40  
  Purchase #4 $201.30   3.151%   $207.643   $207.64   $207.65   $207.60  
  Purchase #5 $211.44   3.283%   $218.3816   $218.38   $218.40   $218.40  
  Purchase #6 $188.34   6.199%   $200.0152   $200.02   $200.00   $200.00  
  Purchase #7 $190.40   5.130%   $200.1675   $200.17   $200.15   $200.20  
  7 purchase totals = $1,115.68       $1,176.5100   $1,176.51   $1,176.50   $1,176.50