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 $212.74   5.446%   $224.3258   $224.33   $224.35   $224.30  
  Purchase #2 $160.58   9.457%   $175.7661   $175.77   $175.75   $175.80  
  Purchase #3 $118.64   9.719%   $130.1706   $130.17   $130.15   $130.20  
  Purchase #4 $157.76   7.706%   $169.917   $169.92   $169.90   $169.90  
  Purchase #5 $95.70   13.231%   $108.3621   $108.36   $108.35   $108.40  
  Purchase #6 $217.97   13.796%   $248.0411   $248.04   $248.05   $248.00  
  Purchase #7 $80.33   4.739%   $84.1368   $84.14   $84.15   $84.10  
  7 purchase totals = $1,043.72       $1,140.7195   $1,140.73   $1,140.70   $1,140.70