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 $84.56   12.865%   $95.4386   $95.44   $95.45   $95.40  
  Purchase #2 $110.35   8.228%   $119.4296   $119.43   $119.45   $119.40  
  Purchase #3 $11.60   3.834%   $12.0447   $12.04   $12.05   $12.00  
  Purchase #4 $88.86   3.176%   $91.6822   $91.68   $91.70   $91.70  
  Purchase #5 $106.65   7.531%   $114.6818   $114.68   $114.70   $114.70  
  Purchase #6 $184.33   4.425%   $192.4866   $192.49   $192.50   $192.50  
  Purchase #7 $114.82   12.110%   $128.7247   $128.72   $128.70   $128.70  
  7 purchase totals = $701.17       $754.4882   $754.48   $754.55   $754.40