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 $54.74   13.754%   $62.2689   $62.27   $62.25   $62.30  
  Purchase #2 $124.61   12.784%   $140.5401   $140.54   $140.55   $140.50  
  Purchase #3 $228.79   9.181%   $249.7952   $249.80   $249.80   $249.80  
  Purchase #4 $67.99   8.862%   $74.0153   $74.02   $74.00   $74.00  
  Purchase #5 $109.68   6.774%   $117.1097   $117.11   $117.10   $117.10  
  Purchase #6 $221.74   13.748%   $252.2248   $252.22   $252.20   $252.20  
  Purchase #7 $117.66   4.634%   $123.1124   $123.11   $123.10   $123.10  
  7 purchase totals = $925.21       $1,019.0664   $1,019.07   $1,019.00   $1,019.00