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 $61.64   5.467%   $65.0099   $65.01   $65.00   $65.00  
  Purchase #2 $248.40   8.114%   $268.5552   $268.56   $268.55   $268.60  
  Purchase #3 $237.50   3.285%   $245.3019   $245.30   $245.30   $245.30  
  Purchase #4 $193.65   13.746%   $220.2691   $220.27   $220.25   $220.30  
  Purchase #5 $116.73   8.340%   $126.4653   $126.47   $126.45   $126.50  
  Purchase #6 $30.58   13.605%   $34.7404   $34.74   $34.75   $34.70  
  Purchase #7 $104.51   5.423%   $110.1776   $110.18   $110.20   $110.20  
  7 purchase totals = $993.01       $1,070.5194   $1,070.53   $1,070.50   $1,070.60