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 $230.26   4.666%   $241.0039   $241.00   $241.00   $241.00  
  Purchase #2 $166.78   11.668%   $186.2399   $186.24   $186.25   $186.20  
  Purchase #3 $236.48   9.222%   $258.2882   $258.29   $258.30   $258.30  
  Purchase #4 $52.99   11.783%   $59.2338   $59.23   $59.25   $59.20  
  Purchase #5 $214.86   5.385%   $226.4302   $226.43   $226.45   $226.40  
  Purchase #6 $71.36   3.295%   $73.7113   $73.71   $73.70   $73.70  
  Purchase #7 $67.35   6.286%   $71.5836   $71.58   $71.60   $71.60  
  7 purchase totals = $1,040.08       $1,116.4909   $1,116.48   $1,116.55   $1,116.40