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 $164.33   3.133%   $169.4785   $169.48   $169.50   $169.50  
  Purchase #2 $141.57   10.653%   $156.6515   $156.65   $156.65   $156.70  
  Purchase #3 $62.75   6.829%   $67.0352   $67.04   $67.05   $67.00  
  Purchase #4 $194.47   3.760%   $201.7821   $201.78   $201.80   $201.80  
  Purchase #5 $179.82   7.162%   $192.6987   $192.70   $192.70   $192.70  
  Purchase #6 $213.56   3.601%   $221.2503   $221.25   $221.25   $221.30  
  Purchase #7 $225.90   11.712%   $252.3574   $252.36   $252.35   $252.40  
  7 purchase totals = $1,182.40       $1,261.2537   $1,261.26   $1,261.30   $1,261.40