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 $179.35   9.253%   $195.9453   $195.95   $195.95   $195.90  
  Purchase #2 $145.89   4.419%   $152.3369   $152.34   $152.35   $152.30  
  Purchase #3 $140.26   10.533%   $155.0336   $155.03   $155.05   $155.00  
  Purchase #4 $219.31   13.203%   $248.2655   $248.27   $248.25   $248.30  
  Purchase #5 $66.47   3.745%   $68.9593   $68.96   $68.95   $69.00  
  Purchase #6 $115.48   13.397%   $130.9509   $130.95   $130.95   $131.00  
  Purchase #7 $239.57   3.535%   $248.0388   $248.04   $248.05   $248.00  
  7 purchase totals = $1,106.33       $1,199.5303   $1,199.54   $1,199.55   $1,199.50