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 $211.48   3.411%   $218.6936   $218.69   $218.70   $218.70  
  Purchase #2 $79.57   3.345%   $82.2316   $82.23   $82.25   $82.20  
  Purchase #3 $14.52   11.170%   $16.1419   $16.14   $16.15   $16.10  
  Purchase #4 $196.72   13.237%   $222.7598   $222.76   $222.75   $222.80  
  Purchase #5 $193.37   4.642%   $202.3462   $202.35   $202.35   $202.30  
  Purchase #6 $232.99   13.736%   $264.9935   $264.99   $265.00   $265.00  
  Purchase #7 $91.30   5.592%   $96.4055   $96.41   $96.40   $96.40  
  7 purchase totals = $1,019.95       $1,103.5721   $1,103.57   $1,103.60   $1,103.50