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 $213.30   3.453%   $220.6652   $220.67   $220.65   $220.70  
  Purchase #2 $31.72   5.109%   $33.3406   $33.34   $33.35   $33.30  
  Purchase #3 $39.81   11.417%   $44.3551   $44.36   $44.35   $44.40  
  Purchase #4 $223.54   3.441%   $231.232   $231.23   $231.25   $231.20  
  Purchase #5 $60.56   5.208%   $63.714   $63.71   $63.70   $63.70  
  Purchase #6 $206.41   9.285%   $225.5752   $225.58   $225.60   $225.60  
  Purchase #7 $222.85   11.642%   $248.7942   $248.79   $248.80   $248.80  
  7 purchase totals = $998.19       $1,067.6763   $1,067.68   $1,067.70   $1,067.70