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 $219.60   11.172%   $244.1337   $244.13   $244.15   $244.10  
  Purchase #2 $124.42   13.508%   $141.2267   $141.23   $141.25   $141.20  
  Purchase #3 $98.25   7.493%   $105.6119   $105.61   $105.60   $105.60  
  Purchase #4 $238.28   10.665%   $263.6926   $263.69   $263.70   $263.70  
  Purchase #5 $41.42   6.146%   $43.9657   $43.97   $43.95   $44.00  
  Purchase #6 $230.68   4.324%   $240.6546   $240.65   $240.65   $240.70  
  Purchase #7 $76.49   11.115%   $84.9919   $84.99   $85.00   $85.00  
  7 purchase totals = $1,029.14       $1,124.2771   $1,124.27   $1,124.30   $1,124.30