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 $48.35   8.867%   $52.6372   $52.64   $52.65   $52.60  
  Purchase #2 $35.67   4.433%   $37.2513   $37.25   $37.25   $37.30  
  Purchase #3 $245.65   12.249%   $275.7397   $275.74   $275.75   $275.70  
  Purchase #4 $206.62   8.406%   $223.9885   $223.99   $224.00   $224.00  
  Purchase #5 $79.58   12.374%   $89.4272   $89.43   $89.45   $89.40  
  Purchase #6 $171.54   11.848%   $191.8641   $191.86   $191.85   $191.90  
  Purchase #7 $227.25   9.529%   $248.9047   $248.90   $248.90   $248.90  
  7 purchase totals = $1,014.66       $1,119.8127   $1,119.81   $1,119.85   $1,119.80