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 $214.60   5.337%   $226.0532   $226.05   $226.05   $226.10  
  Purchase #2 $26.68   6.202%   $28.3347   $28.33   $28.35   $28.30  
  Purchase #3 $52.29   6.534%   $55.7066   $55.71   $55.70   $55.70  
  Purchase #4 $235.29   5.417%   $248.0357   $248.04   $248.05   $248.00  
  Purchase #5 $180.96   9.823%   $198.7357   $198.74   $198.75   $198.70  
  Purchase #6 $98.94   10.666%   $109.4929   $109.49   $109.50   $109.50  
  Purchase #7 $17.36   10.858%   $19.2449   $19.24   $19.25   $19.20  
  7 purchase totals = $826.12       $885.6037   $885.60   $885.65   $885.50