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 $95.76   5.433%   $100.9626   $100.96   $100.95   $101.00  
  Purchase #2 $228.41   13.585%   $259.4395   $259.44   $259.45   $259.40  
  Purchase #3 $151.80   8.342%   $164.4632   $164.46   $164.45   $164.50  
  Purchase #4 $106.68   5.862%   $112.9336   $112.93   $112.95   $112.90  
  Purchase #5 $172.97   12.270%   $194.1934   $194.19   $194.20   $194.20  
  Purchase #6 $80.77   7.795%   $87.066   $87.07   $87.05   $87.10  
  Purchase #7 $46.28   5.864%   $48.9939   $48.99   $49.00   $49.00  
  7 purchase totals = $882.67       $968.0522   $968.04   $968.05   $968.10