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 $168.67   5.326%   $177.6534   $177.65   $177.65   $177.70  
  Purchase #2 $40.61   3.472%   $42.02   $42.02   $42.00   $42.00  
  Purchase #3 $163.41   10.233%   $180.1317   $180.13   $180.15   $180.10  
  Purchase #4 $32.85   5.541%   $34.6702   $34.67   $34.65   $34.70  
  Purchase #5 $88.61   5.258%   $93.2691   $93.27   $93.25   $93.30  
  Purchase #6 $247.32   11.489%   $275.7346   $275.73   $275.75   $275.70  
  Purchase #7 $210.85   13.790%   $239.9262   $239.93   $239.95   $239.90  
  7 purchase totals = $952.32       $1,043.4052   $1,043.40   $1,043.40   $1,043.40