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 $197.83   7.245%   $212.1628   $212.16   $212.15   $212.20  
  Purchase #2 $222.58   6.121%   $236.2041   $236.20   $236.20   $236.20  
  Purchase #3 $129.47   10.715%   $143.3427   $143.34   $143.35   $143.30  
  Purchase #4 $207.67   10.493%   $229.4608   $229.46   $229.45   $229.50  
  Purchase #5 $220.59   6.472%   $234.8666   $234.87   $234.85   $234.90  
  Purchase #6 $222.85   9.208%   $243.37   $243.37   $243.35   $243.40  
  Purchase #7 $68.96   4.193%   $71.8515   $71.85   $71.85   $71.90  
  7 purchase totals = $1,269.95       $1,371.2585   $1,371.25   $1,371.20   $1,371.40