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 $166.93   4.262%   $174.0446   $174.04   $174.05   $174.00  
  Purchase #2 $189.96   13.702%   $215.9883   $215.99   $216.00   $216.00  
  Purchase #3 $48.44   6.697%   $51.684   $51.68   $51.70   $51.70  
  Purchase #4 $114.40   8.299%   $123.8941   $123.89   $123.90   $123.90  
  Purchase #5 $93.74   3.383%   $96.9112   $96.91   $96.90   $96.90  
  Purchase #6 $220.97   7.474%   $237.4853   $237.49   $237.50   $237.50  
  Purchase #7 $206.36   7.675%   $222.1981   $222.20   $222.20   $222.20  
  7 purchase totals = $1,040.80       $1,122.2056   $1,122.20   $1,122.25   $1,122.20