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 $95.47   11.351%   $106.3068   $106.31   $106.30   $106.30  
  Purchase #2 $180.82   13.373%   $205.0011   $205.00   $205.00   $205.00  
  Purchase #3 $239.45   11.135%   $266.1128   $266.11   $266.10   $266.10  
  Purchase #4 $171.93   13.772%   $195.6082   $195.61   $195.60   $195.60  
  Purchase #5 $188.42   8.869%   $205.131   $205.13   $205.15   $205.10  
  Purchase #6 $86.93   5.219%   $91.4669   $91.47   $91.45   $91.50  
  Purchase #7 $235.95   12.748%   $266.0289   $266.03   $266.05   $266.00  
  7 purchase totals = $1,198.97       $1,335.6557   $1,335.66   $1,335.65   $1,335.60