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 $58.51   5.675%   $61.8304   $61.83   $61.85   $61.80  
  Purchase #2 $195.52   3.390%   $202.1481   $202.15   $202.15   $202.10  
  Purchase #3 $43.86   8.310%   $47.5048   $47.50   $47.50   $47.50  
  Purchase #4 $208.51   10.616%   $230.6454   $230.65   $230.65   $230.60  
  Purchase #5 $227.91   6.249%   $242.1521   $242.15   $242.15   $242.20  
  Purchase #6 $95.85   9.723%   $105.1695   $105.17   $105.15   $105.20  
  Purchase #7 $229.55   4.468%   $239.8063   $239.81   $239.80   $239.80  
  7 purchase totals = $1,059.71       $1,129.2566   $1,129.26   $1,129.25   $1,129.20