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 $23.61   8.417%   $25.5973   $25.60   $25.60   $25.60  
  Purchase #2 $208.60   9.316%   $228.0332   $228.03   $228.05   $228.00  
  Purchase #3 $214.34   12.672%   $241.5012   $241.50   $241.50   $241.50  
  Purchase #4 $247.72   11.629%   $276.5274   $276.53   $276.55   $276.50  
  Purchase #5 $183.73   3.492%   $190.1459   $190.15   $190.15   $190.10  
  Purchase #6 $101.96   13.561%   $115.7868   $115.79   $115.80   $115.80  
  Purchase #7 $92.64   8.859%   $100.847   $100.85   $100.85   $100.80  
  7 purchase totals = $1,072.60       $1,178.4388   $1,178.45   $1,178.50   $1,178.30