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 $69.31   5.712%   $73.269   $73.27   $73.25   $73.30  
  Purchase #2 $220.58   12.674%   $248.5363   $248.54   $248.55   $248.50  
  Purchase #3 $162.26   12.638%   $182.7664   $182.77   $182.75   $182.80  
  Purchase #4 $18.91   8.559%   $20.5285   $20.53   $20.55   $20.50  
  Purchase #5 $198.72   13.753%   $226.05   $226.05   $226.05   $226.10  
  Purchase #6 $217.79   9.793%   $239.1182   $239.12   $239.10   $239.10  
  Purchase #7 $71.72   10.163%   $79.0089   $79.01   $79.00   $79.00  
  7 purchase totals = $959.29       $1,069.2773   $1,069.29   $1,069.25   $1,069.30