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 $143.61   9.225%   $156.858   $156.86   $156.85   $156.90  
  Purchase #2 $167.86   5.119%   $176.4528   $176.45   $176.45   $176.50  
  Purchase #3 $146.89   9.606%   $161.0003   $161.00   $161.00   $161.00  
  Purchase #4 $200.68   6.400%   $213.5235   $213.52   $213.50   $213.50  
  Purchase #5 $81.28   4.445%   $84.8929   $84.89   $84.90   $84.90  
  Purchase #6 $114.29   11.447%   $127.3728   $127.37   $127.35   $127.40  
  Purchase #7 $78.55   3.851%   $81.575   $81.58   $81.60   $81.60  
  7 purchase totals = $933.16       $1,001.6753   $1,001.67   $1,001.65   $1,001.80