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 $83.78   13.699%   $95.257   $95.26   $95.25   $95.30  
  Purchase #2 $206.33   11.354%   $229.7567   $229.76   $229.75   $229.80  
  Purchase #3 $214.79   11.765%   $240.06   $240.06   $240.05   $240.10  
  Purchase #4 $50.95   6.849%   $54.4396   $54.44   $54.45   $54.40  
  Purchase #5 $10.95   3.341%   $11.3158   $11.32   $11.30   $11.30  
  Purchase #6 $184.93   9.275%   $202.0823   $202.08   $202.10   $202.10  
  Purchase #7 $182.66   12.493%   $205.4797   $205.48   $205.50   $205.50  
  7 purchase totals = $934.39       $1,038.3911   $1,038.40   $1,038.40   $1,038.50