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 $167.79   10.655%   $185.668   $185.67   $185.65   $185.70  
  Purchase #2 $155.79   10.659%   $172.3957   $172.40   $172.40   $172.40  
  Purchase #3 $104.87   11.273%   $116.692   $116.69   $116.70   $116.70  
  Purchase #4 $162.83   6.129%   $172.8099   $172.81   $172.80   $172.80  
  Purchase #5 $156.90   6.843%   $167.6367   $167.64   $167.65   $167.60  
  Purchase #6 $208.26   4.750%   $218.1524   $218.15   $218.15   $218.20  
  Purchase #7 $218.96   4.167%   $228.0841   $228.08   $228.10   $228.10  
  7 purchase totals = $1,175.40       $1,261.4388   $1,261.44   $1,261.45   $1,261.50