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 $85.97   8.363%   $93.1597   $93.16   $93.15   $93.20  
  Purchase #2 $166.26   4.775%   $174.1989   $174.20   $174.20   $174.20  
  Purchase #3 $108.98   3.864%   $113.191   $113.19   $113.20   $113.20  
  Purchase #4 $250.88   6.204%   $266.4446   $266.44   $266.45   $266.40  
  Purchase #5 $207.56   5.176%   $218.3033   $218.30   $218.30   $218.30  
  Purchase #6 $194.33   7.115%   $208.1566   $208.16   $208.15   $208.20  
  Purchase #7 $48.50   11.723%   $54.1857   $54.19   $54.20   $54.20  
  7 purchase totals = $1,062.48       $1,127.6398   $1,127.64   $1,127.65   $1,127.70