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 $162.25   9.670%   $177.9396   $177.94   $177.95   $177.90  
  Purchase #2 $103.61   8.173%   $112.078   $112.08   $112.10   $112.10  
  Purchase #3 $224.83   4.770%   $235.5544   $235.55   $235.55   $235.60  
  Purchase #4 $185.61   8.277%   $200.9729   $200.97   $200.95   $201.00  
  Purchase #5 $15.59   4.301%   $16.2605   $16.26   $16.25   $16.30  
  Purchase #6 $97.80   3.233%   $100.9619   $100.96   $100.95   $101.00  
  Purchase #7 $159.39   7.152%   $170.7896   $170.79   $170.80   $170.80  
  7 purchase totals = $949.08       $1,014.5569   $1,014.55   $1,014.55   $1,014.70