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 $58.31   4.672%   $61.0342   $61.03   $61.05   $61.00  
  Purchase #2 $33.67   6.773%   $35.9505   $35.95   $35.95   $36.00  
  Purchase #3 $193.72   10.517%   $214.0935   $214.09   $214.10   $214.10  
  Purchase #4 $247.32   6.639%   $263.7396   $263.74   $263.75   $263.70  
  Purchase #5 $185.77   10.497%   $205.2703   $205.27   $205.25   $205.30  
  Purchase #6 $225.26   8.632%   $244.7044   $244.70   $244.70   $244.70  
  Purchase #7 $127.48   7.229%   $136.6955   $136.70   $136.70   $136.70  
  7 purchase totals = $1,071.53       $1,161.4880   $1,161.48   $1,161.50   $1,161.50