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 $192.48   4.408%   $200.9645   $200.96   $200.95   $201.00  
  Purchase #2 $95.40   10.118%   $105.0526   $105.05   $105.05   $105.10  
  Purchase #3 $154.26   6.337%   $164.0355   $164.04   $164.05   $164.00  
  Purchase #4 $66.99   12.215%   $75.1728   $75.17   $75.15   $75.20  
  Purchase #5 $101.34   9.530%   $110.9977   $111.00   $111.00   $111.00  
  Purchase #6 $211.64   10.803%   $234.5035   $234.50   $234.50   $234.50  
  Purchase #7 $200.33   7.218%   $214.7898   $214.79   $214.80   $214.80  
  7 purchase totals = $1,022.44       $1,105.5164   $1,105.51   $1,105.50   $1,105.60