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 $204.35   4.720%   $213.9953   $214.00   $214.00   $214.00  
  Purchase #2 $175.59   10.839%   $194.6222   $194.62   $194.60   $194.60  
  Purchase #3 $192.51   10.559%   $212.8371   $212.84   $212.85   $212.80  
  Purchase #4 $31.30   11.621%   $34.9374   $34.94   $34.95   $34.90  
  Purchase #5 $221.77   4.190%   $231.0622   $231.06   $231.05   $231.10  
  Purchase #6 $51.56   5.689%   $54.4932   $54.49   $54.50   $54.50  
  Purchase #7 $116.25   6.493%   $123.7981   $123.80   $123.80   $123.80  
  7 purchase totals = $993.33       $1,065.7455   $1,065.75   $1,065.75   $1,065.70