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 $241.74   11.432%   $269.3757   $269.38   $269.40   $269.40  
  Purchase #2 $190.55   10.736%   $211.0074   $211.01   $211.00   $211.00  
  Purchase #3 $218.77   5.846%   $231.5593   $231.56   $231.55   $231.60  
  Purchase #4 $202.57   3.618%   $209.899   $209.90   $209.90   $209.90  
  Purchase #5 $234.57   6.807%   $250.5372   $250.54   $250.55   $250.50  
  Purchase #6 $210.45   4.286%   $219.4699   $219.47   $219.45   $219.50  
  Purchase #7 $72.67   3.482%   $75.2004   $75.20   $75.20   $75.20  
  7 purchase totals = $1,371.32       $1,467.0489   $1,467.06   $1,467.05   $1,467.10